Rootkit C:\avast! sandbox


Today I ran a deepscan and AVG found a rootkit in the folder C:\avast! sandbox.…
When I click on "resolve all" in AVG, AVG tells me that it can not resolve the problem. See the pictures below…

I have tried updating AVG and rebooting my PC, but I can not remove this thread. 
Next to this the microsoft edge browser does not work anymore and there constantly is a loading wheel flickering next the pointer of the mouse.

Could you help me remove this thread?
Help is much apricated!
AVG app screenshot