Cannot change language in dashboard (I am the admin)

Hello,

I need some help in changing the language of the dashboard. The website was originally created in Germany, by a German developer and he probably used the DE version of WordPress, I cannot tell. Now I need to run the website from Romania and I do not speak German.

I am admin and I’ve tried, of course, to change the language in Settings/General. In the drop down menu I get 3 languages: Romanian, English and German, but it won’t switch to any of them.

What can I do?
Thank you!