Apple Mail opens blank windows and fails to send email on Macbook Air

Hello, I've asked this before but can't see my topic anymore and had no replies:

Apple Mail keeps popping up empty/blank windows, only shutting down the program stops it (briefly).

I now can't send emails anymore either.

I've tried so far:

• deleting scripts in Library
• force quitted Mail and restarted with Shift
• restarting macbook /Sequoia 15.5)

I'd be so appreciative of any tipps to solve this issue.

Thank you!