diff --git a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
index ce738c33..030e7212 100644
--- a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
+++ b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
@@ -9,21 +9,18 @@
  *   "product": 30 // 2 * 3 * 5
  * }
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: O(N)
+ * Space Complexity: 0(1) - depends on numbers.length
+ * Optimal Time Complexity: O(N)
  *
  * @param {Array<number>} numbers - Numbers to process
  * @returns {Object} Object containing running total and product
  */
 export function calculateSumAndProduct(numbers) {
   let sum = 0;
-  for (const num of numbers) {
-    sum += num;
-  }
-
   let product = 1;
   for (const num of numbers) {
+    sum += num;
     product *= num;
   }
 
diff --git a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
index 5619ae5d..cf9b9f90 100644
--- a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
+++ b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
@@ -1,14 +1,17 @@
 /**
  * Finds common items between two arrays.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: worst O(N1 * N2)
+ * Space Complexity: worst O(N1 + N2)
+ * Optimal Time Complexity: worst become: O(N1 + N2)
  *
  * @param {Array} firstArray - First array to compare
  * @param {Array} secondArray - Second array to compare
  * @returns {Array} Array containing unique common items
  */
-export const findCommonItems = (firstArray, secondArray) => [
-  ...new Set(firstArray.filter((item) => secondArray.includes(item))),
-];
+export const findCommonItems = (firstArray, secondArray) => {
+  const firstSet = new Set(firstArray);
+  const secondSet = new Set(secondArray);
+  const intersection = secondSet.intersection(firstSet);
+  return [...intersection];
+};
diff --git a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
index dd2901f6..7769f9be 100644
--- a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
+++ b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
@@ -1,21 +1,23 @@
 /**
  * Find if there is a pair of numbers that sum to a given target value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: worst O(N^2) - square
+ * Space Complexity: O(1)
+ * Optimal Time Complexity: worth become O(N)
  *
  * @param {Array<number>} numbers - Array of numbers to search through
  * @param {number} target - Target sum to find
  * @returns {boolean} True if pair exists, false otherwise
  */
+
 export function hasPairWithSum(numbers, target) {
+  const checkedNumbers = new Set();
   for (let i = 0; i < numbers.length; i++) {
-    for (let j = i + 1; j < numbers.length; j++) {
-      if (numbers[i] + numbers[j] === target) {
-        return true;
-      }
+    const complement = target - numbers[i];
+    if ( checkedNumbers.has(complement)) {
+      return true;
     }
+    checkedNumbers.add(numbers[i])
   }
   return false;
 }
diff --git a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
index dc5f7711..45949f61 100644
--- a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
+++ b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
@@ -1,36 +1,18 @@
 /**
  * Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: O(N*N) quadratic
+ * Space Complexity: O(N)
+ * Optimal Time Complexity: become O(N)
  *
  * @param {Array} inputSequence - Sequence to remove duplicates from
  * @returns {Array} New sequence with duplicates removed
  */
 export function removeDuplicates(inputSequence) {
-  const uniqueItems = [];
+  const uniqueItems = new Set();
+  inputSequence.forEach((element) => {
+    uniqueItems.add(element)
+  });
 
-  for (
-    let currentIndex = 0;
-    currentIndex < inputSequence.length;
-    currentIndex++
-  ) {
-    let isDuplicate = false;
-    for (
-      let compareIndex = 0;
-      compareIndex < uniqueItems.length;
-      compareIndex++
-    ) {
-      if (inputSequence[currentIndex] === uniqueItems[compareIndex]) {
-        isDuplicate = true;
-        break;
-      }
-    }
-    if (!isDuplicate) {
-      uniqueItems.push(inputSequence[currentIndex]);
-    }
-  }
-
-  return uniqueItems;
+  return [...uniqueItems];
 }
diff --git a/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py b/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
index cfd5cfdf..aff4c9ac 100644
--- a/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
+++ b/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
@@ -12,20 +12,19 @@ def calculate_sum_and_product(input_numbers: List[int]) -> Dict[str, int]:
         "sum": 10, // 2 + 3 + 5
         "product": 30 // 2 * 3 * 5
     }
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
+    Time Complexity: O(N*2)
+    Space Complexity: O(N)
+    Optimal time complexity: O(N)
     """
     # Edge case: empty list
     if not input_numbers:
         return {"sum": 0, "product": 1}
 
     sum = 0
-    for current_number in input_numbers:
-        sum += current_number
-
     product = 1
     for current_number in input_numbers:
+        sum += current_number
         product *= current_number
+        
 
     return {"sum": sum, "product": product}
diff --git a/Sprint-1/Python/find_common_items/find_common_items.py b/Sprint-1/Python/find_common_items/find_common_items.py
index 478e2efc..2f5241dc 100644
--- a/Sprint-1/Python/find_common_items/find_common_items.py
+++ b/Sprint-1/Python/find_common_items/find_common_items.py
@@ -9,13 +9,10 @@ def find_common_items(
     """
     Find common items between two arrays.
 
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
+    Time Complexity: worst O(N1 * N2)
+    Space Complexity: worst O(N1 + N2)
+    Optimal time complexity: worst become: O(N1 + N2)
     """
-    common_items: List[ItemType] = []
-    for i in first_sequence:
-        for j in second_sequence:
-            if i == j and i not in common_items:
-                common_items.append(i)
-    return common_items
+    firstSet = set(first_sequence)
+    secondSet = set(second_sequence)
+    return list(firstSet.intersection(secondSet))
diff --git a/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py b/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
index fe2da517..a1365805 100644
--- a/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
+++ b/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
@@ -7,12 +7,15 @@ def has_pair_with_sum(numbers: List[Number], target_sum: Number) -> bool:
     """
     Find if there is a pair of numbers that sum to a target value.
 
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
+    Time Complexity: worst O(N^2) - square
+    Space Complexity: O(numbers.length)
+    Optimal time complexity: worth become O(N)
     """
-    for i in range(len(numbers)):
-        for j in range(i + 1, len(numbers)):
-            if numbers[i] + numbers[j] == target_sum:
-                return True
+
+    cheked_numbers = set()
+    for number in numbers:
+        complement = target_sum - number
+        if complement in cheked_numbers:
+            return True
+        cheked_numbers.add(number)
     return False
diff --git a/Sprint-1/Python/remove_duplicates/remove_duplicates.py b/Sprint-1/Python/remove_duplicates/remove_duplicates.py
index c9fdbe80..bf251f90 100644
--- a/Sprint-1/Python/remove_duplicates/remove_duplicates.py
+++ b/Sprint-1/Python/remove_duplicates/remove_duplicates.py
@@ -7,19 +7,15 @@ def remove_duplicates(values: Sequence[ItemType]) -> List[ItemType]:
     """
     Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
 
-    Time complexity:
-    Space complexity:
-    Optimal time complexity:
+    Time complexity: O(N*N) quadratic
+    Space complexity: O(N)
+    Optimal time complexity: become O(N)
     """
-    unique_items = []
-
+    added_values = set()
+    result = []
     for value in values:
-        is_duplicate = False
-        for existing in unique_items:
-            if value == existing:
-                is_duplicate = True
-                break
-        if not is_duplicate:
-            unique_items.append(value)
+        if value not in added_values:
+            added_values.add(value)
+            result.append(value)
 
-    return unique_items
+    return result