This largely depends on the practice you put into it. If you are Ding Bai and are now a senior one, then if you can guarantee to practice seriously and efficiently for about 2 hours every day, and your talents are not bad, such as sense of rhythm and intonation, it is estimated to be 5 years.

However, the piano has a lot to learn, not just those graded pieces. Moreover, a really good teacher will not take you to the exam and catch up with the progress, but will only narrow the learning path. While studying music performance, you can also learn a lot of related things, such as music theory, history, development, art theory and so on, which is quite broad.

In addition, even if you have passed grade 9 or grade, there is no preferential policy on things like further studies. Don't be cheated.