17 R5, couldn't remove heatsink assembly screws

Hello!

I have a problem with removing heat-sink assembly screws on motherboard. My colleagues didn't repaste and clean it since they bought it. The laptop is overheating, so I decided to remove dust and repaste it.

I disassembled all screws without any problem except these ones. It seems like they were tightened very strong in factory. I tried to remove one screw but got stripped screw

Here is pictures:

Please help!