Problem with CPU and more

[RCK98]

Hi, i have 2 problems with my laptop (Lenovo Legion y520 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHZ, 8GB RAM, GTX 1050Ti)

I'll try to explain the problems (sorry for my english). 1st problem (i believe) is with my CPU. After playing 3-5 minutes CS GO fps starts jumping from 120 to 30. I downloaded msi afterburner and checked whats the problem. When i'm playing, my CPU and GPU usage are ~30% and CPU temperature is around 80 C. Sometimes GPU jumps to 60% or 70%, but CPU stays at 30%. Whats the problem? Is it because of high temeprature, should i clean dust and change thermal paste, or problem is not temperature? 

 

2nd problem is different. After watching ~10 minutes youtube, netflix or movies using VLC my audio and video gets out of sync. I noticed that if charger pluged off I haven no problems with sync. I tried reinstalling video card drivers, Bios, event reinstalling windows, but nothing helped. I have this problem for a year.