The FPS will at least partially depends on the complexity of graphics that is being drawn. Some models are simple (i.e. the fence) and render quickly, some are more complex (warehouse with cones in front of it) and require more time to render.
The issue with colourful lines is new to me. I will have to look it up. It’s something with blending, most likely.
Thanks for the feedback h3ckboy 
I enabled the console, started the game and boom: it worked normally.
Nothing was printed to the console. Don’t know what that problem was before, I tried twice and it just quit before showing anything apart from a white window.