The topic titles are 33 characters which is very small. What file do i need to edit to allow to show up more characters on titles when a user browsing the forum?

Its probably user.css using white-space:nowrap;

I think you cut it and save it to mysql cutted because when i check the source code in front in forum i see something like this on topic list:

<a href="https://www.kalosex.com/el/forums/topic/trelo-sex-sto-gymnastirio-i-archi-t17">Τρελό σεξ στο γυμναστήριο!! - ...</a>   (thats a link to a forum topic)


So it seems like it's cutted and saved on mysql and added the three dots in the end. I will check the mysql and will come back to this

I see.
Go to form/board.php
Find line:
<a href="<?php echo frm_topic_url($topic); ?>"><?php echo osc_highlight($topic['s_title'], 30); ?></a>
Replace with:
<a href="<?php echo frm_topic_url($topic); ?>"><?php echo osc_highlight($topic['s_title'], 90); ?></a>