Форум поддержки Thunderbird

My emails are threading up, even ones that have nothing to do with each other. I've tried 'collapsing threads' in the 'view' menu, but it doesn't seem to help. With so much threading going on, I can't even find some of the new emails that I am alerted to.

I'm a newbe Thunderbird user making the transition from Outlook which I've used for years but recently discovered is too compromising especially when it comes to archiving. Have been using Mozilla for years on a Surface laptop (windows 11), Cyberpower desktop (windows 10), and Android Note 20. I've downloaded Thunderbird and it is working fine. Where can I find user training videos for Thundbird, especially archiving? Are there other ways besides on-line gifting in which I can contribute to the research that makes Mozilla and Thunderbird possible? Thank you.

Emails with different subjects are getting threaded together. For example, in the attached snapshot, why are the emails with subject "Bid S011090833" getting threaded under "Hein Revised Hall Bath..."?

Perhaps I don't understand how Thunderbird determines messages have a common thread.

Using Thunderbird 115.4.1 (64-bit)