Hi zhuravliov,
When trying to watch a video full screen, a flickering screen makes anything difficult to watch. Let’s try to find out what’s causing this behavior.
You didn’t mention any steps you have tried, so we recommend starting here.
First, see if this flickering continues in safe mode. When starting up in safe mode, it is normal to take longer than a normal start up. Safe mode is doing a check like First Aid. See How to use safe mode on your Mac for details.
If the flickering continues in safe mode, see How to reset the SMC of your Mac.
Should the behavior continue, try setting up another account on your MacBook Air to see if this happens only in your account or both accounts. See Set up users, guests, and groups on Mac for details.
Reach back out if you still need help.
Have a great week!