Hi Moritz,
The reason why the contact section is not taking up the full view width of the screen is because your section class has a padding of 60px. I would create a combo class for the contact section and remove the padding — that way your other sections aren’t affected that do require padding.
As far as your second problem is concerned, I’m not sure what the problem is. If you want alignment to be consistent throughout different sections then I would recommend using the same margin/padding amounts throughout different sections of your design.