Hi kage04 and Anfesave!
Game developer here.
Every time player damages an enemy gains XP. The problem was (because of a bug) the server didn't notified the player that his XP changed unless the player changed to a new server.
The good news is (thanks to your report here) we just fixed that problem!
Now your XP should be updated every time you hit an enemy.
Thanks for reporting us this bugs.
Please, if you have any other bug, comment don't hesitate to send us an email to (support@mego.cl) or comment here.