Well i have done some quest, im lvl 30 now but the bosses/mobs are kinda strong xDu, any guide to lvl up proper?
Just follow the main quest and do All the side quests you can find. Search well in the maps!
Level 30 bosses strong? Certainly there are some that are, but they are easy to take down. I would take you messed up your build or your stats.
Err how easy someone takes down a boss does depend on their class. Also depends on whether people are enhancing their weapon. I recommend you find a good weapon every 10 levels or so and just enhance it up as much as you can, it speeds up the process a lot.
Also you might wanna consider just partying up as well. I was around tenet chapel floor 1 around lvl 30 I think, and those levels were a breeze for me because I had a swordsman front-lining.
So far not a problem on bosses on any of my chars (Wiz, Cleric, Archer), but yes, enhancing the gear also helps, specialy the armor and accessories.