To quickly change emails to “read” status in gmail, I tap on emails (opening them) and when in the email I either swipe right or tap the back arrow to return to inbox. I like to do many of these in quick succession to get rid of the amount of unread emails I have.
Once an email is opened, it freezes on the opened page and I have to exit the Gmail app to unfreeze it. About every second or third email in a row is freezing
For help with the Mail app, please post in the Apple Support Community. The Apple Developer Forums are for questions about APIs and features intended specifically for developers.