Videos in an early 2021 version of FahrAPP did sometimes not run correctly on Android smartphones with 64-bit ARM processors. We published a new version in late February.
If you have updated and still having issues, please delete FahrAPP first / deinstall it and download it again.
The current version in 32-bit has no issues at all - again, please deinstall first, then install again:
Thanks and have fun with your training!