I'm level 19 and so far i havent done any of them. The only ones i have done are the ones that you have to enter a wormhole, that tranporsts you to a location, like whehn goku arrived to earth , the world tournament where chichi and goku meet again etc. is this the story quests? or when do i travel with trunks ?

Once you reach 25 you can do a time quest (its here http://www.dbocom.com/atlas.php?do=i...843qiw2qiw1qrr )
It is about Raditz landing on Earth and about a guy called Android 8000 (really strong boss), I would at least have a full party of 25s including a wonder majin and a dragon clan to do easy.

hey is your game korean? you should at least made 2 time quest .. go to your scouter and press 2 look for the red lights those are quest that you should do I think try to do those and some of then will guide you to the time quest good luck