hey there,
if you want to hang out in KL for 4-5 days , you may want to visit these places

Sunway Lagoon- great water theme park with roller coasters. Great bars to hang out at night as well. Theres also a big mall beside it with countless fast-food and restaurant outlets!
(i loved the krispykreme donuts i got from there)

Genting Highlands - well-known for 1)casinos 2) Themepark 3) cool relaxing atmosphere

Chinatown - in the heart of KL - good food and cheap fake goods

Berjaya Times Square - Cool indoor themepark! Largest shopping mall in Malaysia

Petronas Twin Towers - Once the tallest structure in the world


hope this helped