Good afternoon, MarceeNavy
The server has a fast character leveling mode, so in some missions you get 10-20% of experience from your current level. This is normal.
Some quests open only after completing the previous ones. If you want to go through a lot of quests, then go through all. But do not forget about the priority of quests for pumping a profession at levels 20, 40, 60.
There are alternative ways to level up quickly, but that's a different question.
