The question on Bitcoin is answered (copy your date dir to an external drive or usb stick).

What I want to add is that in mid-October Win10 will go out of support and then you may want to upgrade again. Plus, I would give more attention/research on what could have caused your SSD issues and your lag, just blaming it on Win11 makes no sense to me. So you may want to reconsider this "going back to Win10". I am telling this because I find your "solution" a wasted effort: I expect you'll go to Win11 soon.
Of course, it was just an advice; you do as you think it fits, it's your hardware and your time.