Adjusted map 3 and a bit of performance enhancement

As I've been playing the third level a bit myself, I feelt like it might be a bit to difficult. So I made some minor adjustments to it to make it a bit easier.

I've also updated the rendering code, before the game would render the whole image - including the things underneath the GUI at the bottom which then simply got overwritten by the GUI (displaying health and such). It might not seem like a lot of pixels to save there, but it does make a difference. The game runs a bit smoother after this.