Tips for your level up
If you found you complete your main quest at Lvl.15, but you haven’t reach certain level to continue your quest, you need complete 1 or 2 side quests to get enough EXP to help you keep your main quest
Just build a new ship and upgrade it to 10, you can continue your main quest again! But please notice that you may find you are lack of materials, you need go beat some enemies to get materials to build your ship.
You are Lvl.19 now, and your main quest requires Lvl.20 to keep going, but your EXP is just about half to upgrade, so what to do now?
The answer is: side quests! It is the most effective to gain loads of EXP and gold, meanwhile, you can also get a better understanding to this game.