@Gabriel.de Run YouTube for as long as you can or carry out some other screen intensive operation. This will heat the GPU/CPU and screen and may through up an issue. If it happens within 5 minutes, your hardware may be at fault. If it the issue takes a long while to manifest, it can be normal for the aging device. The battery can also affect this if it is weak or failing. The screen is usually the first part along with power button to be damaged through misuse, but is usually the last item to fail through normal use.