Dell g5 freeze and other problems

I purchased dell g5-5587 one year ago and i barely use it.

But now it keeps freezing while watching videos and browsing and sometimes a buzzing sound with freezing

I've tried many solutions and updated all the drivers and nothing works.

Second problem is that few times battery is full charged and laptop doesnt turn on and I've to plug ac and press few times on power button.

Note" tried diagnostics and it tells me that there is no problem"

And i cant get it back to warranty because warranty of any company in egypt is the worst and doesnt solve any thing.

Please help