Hi, ive just begun working on a advanced project.
Il just go right to it, you arrive with the elevator but the path is block so you find a way around the elevator blablabla... I need help with the theme behind the scenes, with walkways and those things... What do I need to have there so it looks realistic?

Just play the single player campaign and look at some of the maps there for inspiration?

https://developer.valvesoftware.com/wiki/Behind_the_Scenes_(Portal_2)