I'm in the process of learning WordPress in order to take over the website of the company where I work, which has not been maintained since 2021.

I'm currently trying to switch to https and install an SSL certificate. Without success so far. As a result, I seem to have made an irreversible mistake.

I tried to change "http://domainname.de" to "https://domainname.de" with the Better Search Replace plugin, but I seem to have forgotten the colon in "https//"…

now if you entering “domainname.de” it no longer goes to the website but tries to reach to "https//domainname.de" without the colon and without success obviously and i get an internal server error 500…

However, but if you manually put the colon in the adress line int he browser it works.
The Google search result also leads to the broken link.

I've tried a number of options with Better Search Replace to undo this, but to no avail. (tried to search out for the without colon one and change it back, but without success)

How do I make “domainname.de” lead back to the actual page???

EDIT:
i did a backup right before that, but even after going back to the backup, it goes to the wrong https// link.
PLEASE HELP!

Thank you!