Multi-site Dashboard not loading for subsites

I think I’ve messed up the whole installation.

The shortest way I can think of is to delete the entire installation (if that is possible) and restart. Is that possible if I want to use back the same domain names?

If so, can anyway share / advise what’s the best way to start afresh?

Otherwise, here’s a history on how it all started
– installed wordpress in a subdomain
– decided to install multisite and reading the documentations I realised I had to have wp installation in the root folder
– moved wordpress from subdomain (subfolder) to root folder. changed siteurl (subdomain) and wordpress url (root domain) in settings **i suspect this is where it all started
– followed instructions to start the multisite installation. (so at this point, siteurl and wordpressurl are not the same)
– multisite enabled
– added new subdomains.
– couldn’t access dashboards of subdomains.

Do I need to copy some files to the subdomains directories?

I really would like to redo this whole thing yet I dunno where to find the answers to start …

Thanks in advance