I think you are getting off the subject. Could we get back to the main point, please?
我觉得你跑题了。 我们能不能回到主题上来?
My brother wants to learn how to play the piano.
我的兄弟要去学弹钢琴。
I am sorry that you have a disagreement with your father. Personally, I think it is important to follow your interests and your abilities, and it sounds as though you have plenty of both of these already.