[Koha] Please help this newbie :)

Hello. Thank you for adding me to this mailing list. I have a question. I am a sysadmin in St Petersburg, Russia and we are in the process of moving to Koha. So I am a newbie :) I chosed the unimarc option as our database is in rusmarc. We have our database in .mrc format, it is about 27 000 books in cyrilic, english and german. I was able to setup koha import that database but the search function does not work. I did a lot of googling, i tried kooha 16.05, 16.11, 17.05 on Debain 8 and 9 but without avail... Any help will be truly appreciated! as i am truly stuck.