Can't upload backup

I had to reinstall everything again because I ran into some problems.

  1. Do I need to finish the setup and activate my new account? Or can I just wait to build Discourse the first time with ./discourse-setup and restore the backup directly?

  2. After restoring the backup it seems that everything is ok (except the missing plugins). I don’t use the default theme but in the other theme the header is missing (after the backup was restored) so I can’t login. I tried to set in the Rails console the default theme Path of theme components - #16 by Osama but after that the site won’t load anymore.

How can I set my account to the default theme so I can lgin again?