Hiya Capricho53,
Thanks for deciding to reach out to the Apple Support Community. We understand that you're having issues in the Overdrive app when using your Brydge 12.9 keyboard. We're happy to assist you with that.
This article is great for troubleshooting unexpected behavior with third-party apps so we recommend you give that a try: If an app unexpectedly quits, stops responding, or won’t open
Although you may not see your specific issue mentioned in the title of that article, the troubleshooting steps will still be relevant.
Also, if your iPhone supports it, please make sure it’s running iOS 13.7: Update your iPhone, iPad, or iPod touch
If you’ve tried the steps in that article and are running the latest iOS update your iPhone can handle, reach out here for additional support: Get Support
Wishing you the best!