A couple of more questions, along with some suggestions:
1. Have you ever done any disk cleanup/maintenance/repairs, from a software perspective? You actually can do a good amount of disk cleanup on your own, and there are some excellent programs available (both free and commercial) that can assist you in those efforts. Along with that, how much free space is on your internal drive?
2. This is
critical: are you making backups to an external device?
3. Do you have the latest version of Mail for Lion?
4. Here are some free programs you can download to clean some things out:
Onyx -
https://www.titanium-software.fr/en/onyx.html (make sure you get the correct version, which is V2.4.8)
AppCleaner -
https://freemacsoft.net/appcleaner/ (again, make sure you get the correct version, which is V2.3)
GrandPerspective -
http://grandperspectiv.sourceforge.net/ (again, make sure you get the correct version, which is V1.7)