Hello Lyftoff,
Try checking to see if the option for 'Offload Unused Apps' is enabled. If this is on the device may automatically remove apps that aren't used recently. This option can be found in Settings > App Store > Offload Unused Apps.
This page can also help to see if the storage on the device is low to help manage that, to rule that out as a cause: How to check the storage on your iPhone and iPad - Apple Support
For issues with the Gmail password you may try reaching using the Gmail Help page for assistance with their service. They'll be in the best position to assist with that particular part. We were able to help locate the Gmail Help page here: Gmail Help
Cheers.