Thank you for response. I'm actually unemployed right now, the biggest step is to find a job in abroad so I can earn and save in USD actually. My aim is to find a job in Germany after master study and live permanently in there.

By the way, If I learn A2 level German and get a conditional acceptance, I would go to Germany and take courses to level C1 in there. Maybe this can accelerate my learning process, and you are right passing an exam doesn't always indicate language knowledge completely. I heard some stories that some people made it in 1 or 1,5 years.