Goes into windowed mode after anticheat loads - then crashes.

@Robinn0r Try those steps also and update us please after testing !
Windows Check:
Press Windows key + 'R' ,typ CMD
Press and hold down CTRL + SHIFT and press ENTER.
When User Account Control shows up, click Yes.
Use the following command lines, pressing Enter after each
(make sure you wait till each of the commands is executed properly):

sfc /scannow
DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth
Reboot your system. (Tell us if errors are fixed)

Drivers update
Check the Youtube movie how to install , download and update ALL drivers.
https://youtu.be/6UpzenfVOAA
Open the web browser and enter url: https:\\www.drivereasy.com

Some drivers updates need to reboot your system, reboot system when needed,
continue using Driver Easy untill 'ALL' drivers are updated.
This free version allows only 1 download and 1 update at once
Reboot system after all updates are done

Network reset::
Press Windows key + 'R' ,typ CMD, Press and hold down CTRL + SHIFT and press ENTER.
When User Account Control shows up, click Yes.
copy and paste the following commands by pressing enter at the end of each command line:

netsh winsock reset
netsh int ip reset
netsh advfirewall reset
netsh winhttp reset proxy
ipconfig /release
ipconfig /flushdns
Reboot your system.

Any app that uses network , and is started for the first time after this reset
a FIREWALL message will popup , grand PUBLIC acces.

(some times you dont see this message then press and hold down ALT and press TAB)