Today I made backup of database, and tried to rename table prefix.
Site works, but if you go directly to topic, if you open site to home page, it redirects to /wp-admin/install.php :(
I will try to restore database back to old version. But if there is solution for this, I would rather have prefix database changed. Thanks.
Deactivated some plugins, Wp total Cache for example, re-activated, cleared cache, and now it works.
Sorry to be so fast on trigger. Thanks.