diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..ccce7f478 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,8 @@
 // Predict and explain first...
 
+// It will print undefined because address[0] looks for a property named "0", which doesn't exist in the object.
+// We can use dot notation (address.houseNumber) to access the correct property.
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +15,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..c221b74e5 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,4 +1,5 @@
 // Predict and explain first...
+// TypeError because object is not iterable and using for of loop in the same way like with arrays won't give us the expected result.
 
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
@@ -11,6 +12,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..22fecba9a 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,4 +1,5 @@
 // Predict and explain first...
+//It won't print ingredients in the new line as we did not located it and we have to use for loop on an array to log it on new lines.
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -11,5 +12,7 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:`);
+for (const ingredient of recipe.ingredients) {
+  console.log(`* ${ingredient}`);
+}
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..0f240e203 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,8 @@
-function contains() {}
+function contains(object, key) {
+  if (typeof object !== "object" || Array.isArray(object) || object === null) {
+    throw new Error("contains requires an object");
+  }
+  return Object.hasOwn(object, key);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 719272787..ca6d65264 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,21 +20,43 @@ as an array isn't an object
 // When passed an object and a property name
 // Then it should return true if the object contains the property, false otherwise
 
+test("when passed an object and a property name, should return true", () => {
+  expect(contains({ name: "Bart" }, "name")).toBe(true);
+});
+
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("when passed empty object to contains returns false", () => {
+  expect(contains({}, "name")).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("when passed to contains with an existing property name, should return true", () => {
+  expect(contains({ name: "Bart", age: 28 }, "age")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("when passed to contains with a non-existing property name, should return false", () => {
+  expect(contains({ name: "Bart" }, "city")).toBe(false);
+});
 
 // Given a value that isn't an object - an array, a string, a number,
 // null, or no argument at all
 // When passed to contains
 // Then it should throw Error("contains requires an object")
 // (careful: typeof [] and typeof null are both "object")
+
+test("throws an error when passed not an object", () => {
+  expect(() => contains(33)).toThrow(/^contains requires an object$/);
+  expect(() => contains("string")).toThrow(/^contains requires an object$/);
+  expect(() => contains(["an array", "with", "some", "data"])).toThrow(
+    /^contains requires an object$/
+  );
+  expect(() => contains(null)).toThrow(/^contains requires an object$/);
+  expect(() => contains()).toThrow(/^contains requires an object$/);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..aff61567f 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,12 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  const pairsFound = {};
+  for (const pair of pairs) {
+    const country = pair[0];
+    const currency = pair[1];
+
+    pairsFound[country] = currency;
+  }
+  return pairsFound;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..9436997f5 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,16 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a country currency code lookup for multiple codes", () => {
+  const pairs = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  expect(createLookup(pairs)).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..1fdb417d8 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -4,10 +4,25 @@ function parseQueryString(queryString) {
     return queryParams;
   }
   const keyValuePairs = queryString.split("&");
-
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    if (pair === "") {
+      continue;
+    }
+    // const [key, value] = pair.split("=");
+
+    const equalsIndex = pair.indexOf("=");
+    let key;
+    let value;
+    if (equalsIndex === -1) {
+      key = pair;
+      value = "";
+    } else {
+      key = pair.slice(0, equalsIndex);
+      value = pair.slice(equalsIndex + 1);
+    }
+    const decodedKey = decodeURIComponent(key.replaceAll("+", " "));
+    const decodedValue = decodeURIComponent(value.replaceAll("+", " "));
+    queryParams[decodedKey] = decodedValue;
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 328b8df61..a2f400262 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,7 +3,7 @@
 // Below are some test cases the implementation doesn't handle well.
 // Fix the implementation for these tests, and try to think of as many other edge cases as possible - write tests and fix those too.
 
-const parseQueryString = require("./querystring.js")
+const parseQueryString = require("./querystring.js");
 
 test("should parse values containing '='", () => {
   expect(parseQueryString("equation=a=b-2")).toEqual({
@@ -36,13 +36,3 @@ test("should replace '+' by ' '", () => {
     "full name": "John Doe",
   });
 });
-
-// Stretch exercise: Handling query strings that contain identical keys
-
-// Delete this test if you are not working on this optional case
-test("should store values of a key in an array when the key has 2 or more values", () => {
-  expect(parseQueryString("key=value1&key=value2&key=value3&foo=bar")).toEqual({
-    key: ["value1", "value2", "value3"],
-    foo: "bar",
-  });
-});
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..b2487dedf 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,16 @@
-function tally() {}
+function tally(array) {
+  if (!Array.isArray(array)) {
+    throw new Error("tally requires an array");
+  }
+  const unique = {};
+  for (const arr of array) {
+    if (Object.hasOwn(unique, arr)) {
+      unique[arr] += 1;
+    } else {
+      unique[arr] = 1;
+    }
+  }
+  return unique;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index ca763c296..04ad3bf0b 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,36 @@ const tally = require("./tally.js");
 // Given a function called tally
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
+test("when given an array of items, should return object with count of each duplicate items", () => {
+  expect(tally(["b", "a", "b"])).toEqual({
+    a: 1,
+    b: 2,
+  });
+});
 
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("given an array with duplicate items, should return counts for each unique item", () => {
+  expect(tally(["a", "a", "a"])).toEqual({
+    a: 3,
+  });
+});
 
 // Given an invalid input like a string, a number, or no argument at all
 // When passed to tally
 // Then it should throw Error("tally requires an array")
+test("given an invalid input like string, number or no argument at all, should throw error('tally requires an array')", () => {
+  expect(() => tally("string")).toThrow(/^tally requires an array$/);
+  expect(() => tally(331)).toThrow(/^tally requires an array$/);
+  expect(() => tally()).toThrow(/^tally requires an array$/);
+  expect(() => tally({})).toThrow(/^tally requires an array$/);
+  expect(() => tally({ a: 3, b: 5 })).toThrow(/^tally requires an array$/);
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..8721d599a 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -7,23 +7,52 @@
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
 function invert(obj) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    throw new Error("input has to be an object");
+  }
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
-
+console.log(invert({ a: 1, b: 2 }));
 // a) What is the current return value when invert is called with { a : 1 }
+//{key:1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+//{key:2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+//{1:a, 2:b}
 
 // c) What does Object.entries return? Why is it needed in this program?
+//Object.entries() returns an array of key-value pairs from an object.
+//We need it in this program to loop through the object's properties and access both the keys and values, so we can swap them.
 
 // d) Explain why the current return value is different from the target output
+//The current output is different because dot notation creates a property called "key" instead of using the variable.
+//Each iteration overwrites the previous value, and the original keys and values are not swapped.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+//fixed, should I make a new file with tests or just add them below as I did?
+
+test("when given single input should invert key and value eg. 'a:1', return '1:a' ", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});
+
+test("when given multiple inputs should invert key and values correctly ", () => {
+  expect(invert({ a: 1, b: 3 })).toEqual({ 1: "a", 3: "b" });
+});
+
+test("when given input type of number, should throw error", () => {
+  expect(() => invert(22)).toThrow(/^input has to be an object$/);
+});
+test("when given input type of string, should throw error", () => {
+  expect(() => invert("22")).toThrow(/^input has to be an object$/);
+});
+test("when given input with different types of than object, should throw error", () => {
+  expect(() => invert([22, 33, "ppp"])).toThrow(/^input has to be an object$/);
+});