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:
GeForce Experience
Riva Tuner
MSI Afterburner
MSI Gaming app
Fraps
Uplay
etc.
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/