Hey Mike, thanks for your reply.
I have solved the problem by changing the settings for the last two hours.
Problem was (hopefully) in my File – Properties – Pixel Format…it was set to 8-bit (like always, since it allows me to work more fluidly on my not so great laptop). After I set it to 32-bit, full range, the problem gone.
I will try to post a short video of how it looks with 8-bit and with 32-bit.