Hi Jessie, thank you for your answer. What you explain is quite typical of L2 learners: we spend many years trying to learn a language but not always successfully. Having said this, if you are talking about your L2 English, I think you’ve done a pretty good job as you can participate in forums in English quite well! ;)
You’ve mentioned some good points about the importance of the environment, the type of focus given to different skills in your lessons as a student (e.g. speaking & listening vs writing & reading) and the interests of the learner. All these factors have an impact on how successfully a second language is learnt.