diff --git a/Week04/decorators_aleyna_gultekin.py b/Week04/decorators_aleyna_gultekin.py
new file mode 100644
index 00000000..e74c73fd
--- /dev/null
+++ b/Week04/decorators_aleyna_gultekin.py
@@ -0,0 +1,32 @@
+import time
+import tracemalloc
+
+
+def performance(fn):
+    """
+    Decorator that measures the execution time and memory usage of a function.
+    Statistics are kept in performance.counter, performance.total_time
+    and performance.total_mem.
+    """
+    def wrapper(*args, **kwargs):
+        tracemalloc.start()
+        begin = time.time()
+        try:
+            output = fn(*args, **kwargs)
+        finally:
+            end = time.time()
+            used = tracemalloc.get_traced_memory()[1]
+            tracemalloc.stop()
+            performance.counter += 1
+            performance.total_time += end - begin
+            performance.total_mem += used
+        return output
+
+    wrapper.__name__ = fn.__name__
+    wrapper.__doc__ = fn.__doc__
+    return wrapper
+
+
+performance.counter = 0
+performance.total_time = 0
+performance.total_mem = 0
diff --git a/Week04/functions_aleyna_gultekin.py b/Week04/functions_aleyna_gultekin.py
new file mode 100644
index 00000000..07f59ea4
--- /dev/null
+++ b/Week04/functions_aleyna_gultekin.py
@@ -0,0 +1,38 @@
+custom_power = lambda x=0, /, e=1: x ** e
+
+
+def custom_equation(x: int = 0, y: int = 0, /, a: int = 1, b: int = 1, *, c: int = 1) -> float:
+    """
+    Raises x to the power a and y to the power b, adds them and divides by c.
+
+    :param x: Base of the first term (positional-only)
+    :type x: int
+    :param y: Base of the second term (positional-only)
+    :type y: int
+    :param a: Power applied to x
+    :type a: int
+    :param b: Power applied to y
+    :type b: int
+    :param c: Number to divide the sum by (keyword-only)
+    :type c: int
+    :return: The calculated value
+    :rtype: float
+    """
+    for name, value in (("x", x), ("y", y), ("a", a), ("b", b), ("c", c)):
+        if type(value) is not int:
+            raise TypeError(f"{name} must be an int")
+    return float((x ** a + y ** b) / c)
+
+
+def fn_w_counter() -> (int, dict[str, int]):
+    if not hasattr(fn_w_counter, "call_count"):
+        fn_w_counter.call_count = 0
+        fn_w_counter.callers = {}
+
+    fn_w_counter.call_count += 1
+    if __name__ in fn_w_counter.callers:
+        fn_w_counter.callers[__name__] += 1
+    else:
+        fn_w_counter.callers[__name__] = 1
+
+    return fn_w_counter.call_count, fn_w_counter.callers