Momentary keyboard problems, zoom problems, the PC switches off by itself

Model: Aspire A515-51G
I bought it in 2018
I use good WiFi connexion
Use: everyday, specially now (study purposes)
Programs that I use: Google Chrome, Word 365, Xodo PDF

momentary keyboard problems, zoom problems, the PC switches off by itself

All of this occurs only for some minutes and then everything gets back to normal, but I have to fix it because I will have online exams with limited time.

I put the 2 windows manually or with Windows +< (or Windows + >)

It is a laptop and I use a bluetooth keyboard. When the keyboard does not respond, both keyboards are affected: the bluetooth one and the proper keyboard

The zoom works by itself when I use the mousewheel and that interupts my work.
How can I deactivate the zoom when this occurs? I never use the trick ctrl+mouse wheel.

The PC is permanently plugged in because if not it turns itself off. However it works 95 % of the time really well. I wanted to have it repaired but the man from the shop told me that batteries always end up to break down.

I hope that you can help me. Thanks in advance. :)