This helped me with the Gmail Problem
https://xiaomi.eu/community/threads/no-gmail-push-notification.50470/#post-536527
THX @Poney70 for posting the Thread :)
Gyroscope, Accelerometer and Compass/ Magnetometer doesn´t Work in Apps and Games on the Redmi Note 8. In CIT Test is everything OK.
UPDATE:
It works again after a reboot.