@ayalak post some examples of your work and references or what is your goal. It will be easier to understand what you mean by good line quality. What is good for one artist may not be good for another. And artists with terrible line quality could be considered great artists compared to those with perfect/good/ideal line quality. Training takes time, it depends on what/how you are doing and if you are supposed to do this activity and if you really have the will to do it etc. etc. Maybe you reach your goal in a very short time or in a couple of years or decades. Would you be willing to train for decades?