My mail keeps crashing and I don't know what to do

Please read and follow If Mail unexpectedly quits when viewing certain messages - Apple Support.

Step 1 is most important because it will cause Mail to open with no particular message selected. Mail might be crashing due to a malformed email message, and that will help isolate the cause.

Thanks. The next step would be to determine if the same problems occur in "Safe Mode": Use safe mode to isolate issues with your Mac - Apple Support.

The inability to post the crash report to the site due to disallowed characters is an annoyance, but the crash report might not help anyway.

This is what I'd do: temporarily delete one or more email account(s) using System Preferences > Internet Accounts, and subsequently add them again.

If that does not help, I'd reinstall macOS: How to reinstall macOS - Apple Support. If that sounds like grasping at straws, that's because I am. Doing so is harmless although I doubt it will fix that particular problem.

Needless to say, if you are using any non-Apple "anti-virus", "cleaning", or "Internet security" junk, anything at all in that broad category of useless garbage, don't. A lot of things won't work if you do. Restarting your Mac in "Safe Mode" should have obviated that concern, and I'm mentioning that only because the symptoms you describe are usually associated with the use of such things.