Sorry to hear of your troubles ... but ... it happens! :\
Adam did suggest appropriately, me thinks ... + 1 Adam!
Starting over might be best at this point.
Issue might have been ...
"Softaculous" for the 3.6 install, but then did the manual for 3.7 upgrade"
Softac is a commercial product (code is not open sourced) provided by your hosting service. If made available to customers, seems to me if there are issues with
whatever app was installed by Softac, provider and Softac should exhaust their expertise in finding out why then suggest Community forums at Moodle.
If the 3.6.x never worked right, upgrading to next version up may not fix. That goes for all of us!
For future postings ...
Before reporting an issue, gather some technical info you can share in these forums.
Descriptions as you've provided, but also ...
Where you host and what level of hosting .. shared server, VPS?
Operating system
PHP version
MySQL version
Much of that information can be seen in Moodle's Admin -> Server -> PHP info.
If moodle was installed and running, turn on debugging, try whatever is not working, come back to forums and post a description of issue and provide a clip of the debug.
https://docs.moodle.org/37/en/Debugging
Many times Google is your friend and searching via Google might hit on a forum discussion here in community forums as well as other blogs .. if nothing else, hints ... but hopefully, solutions.
If an upgrade, did you research if your setup had what it needed by running the Environment Check in moodle?
https://docs.moodle.org/37/en/Environment
BTW, the moodle file system is kinda complicated ... files that are uploaded are uploaded to moodledata/filedir but there is also entered into moodle db mdl_files table a bunch of meta data - which is what is used to generate links to files. While one can see and browse what's in moodledata/filedir/ via cPanel file manager one will note there is no file in there that is humanly re-cognizable any more ... ie, you won't find a graphic file by humanly re-cognizable name, but by query of DB/mdl_files table.
Starting over does mean one thing ... you've learned (maybe) what doesn't work and that's a plus ... frustrating sometimes ... but a plus!
'spirit of sharing', Ken