I cannot open up my Gmail since I did the IOS 15 update

I can open those apps on my iOS/iPadOS 15 devices. Thus something else is at play.

Things to try that will help us help you more:

1. Restart the device
2. Uninstall the app and reinstall it.

If you still see issues after number 1, do number 2.

If neither solves your issue, let us know.

Have you tried restarting your iPad, or uninstalling and reinstalling the app?