1. Please make sure your PC meets minimum system requirements.
2. Add GWENT: Rogue Mage files to the whitelist of your antivirus and firewall.
3. Disable all unneccessary apps before launching the game (especially apps with overlay) such as:
MSI Gaming app
4. Try launching the game in clean boot mode to check if applications running in the background are interfering with the game.
Here is a guide how to perform clean boot: https://support.microsoft.com/en-us/kb/929135/