If you experience crashes, black screens, or performance problems while playing the game on iOS, follow the troubleshooting steps below.
1. Make sure GWENT is up to date, this article explains how to update apps on iOS https://support.apple.com/en-us/HT202180
2. Make sure also that your iOS version is updated to the newest version https://support.apple.com/en-gb/HT204204
3. Shut down other apps running in the background, this article explains how to do it https://support.apple.com/en-us/HT201330
4. Change Wi-Fi connection to cellular, or the other way around (if you use Wi-Fi make sure nothing is interfering with the stability of your connection, e.g. downloads/uploads, streams, other users).
5. Restart your device.
6. If the steps above won't help, try reinstalling the game.