Help me about Mod Plz :) [Newbie]

I want to Mod Map of game Mstar Online from Nurien with Unreal Engine 3…
Anyone can Help me ? the file extension is .umap
I want change some map to be simple cause some my friend got very laggy (cause they have not powerful enough PC)
please help me, if you know.
Thanks alot

This is a forum for Unreal Engine 4, for games you need to look for the forum for that game and talk about it there.