我擅長跳舞，但不會彈鋼琴，李若妍擅長彈鋼琴但不會跳舞

1) I'm good at dancing but not at playing piano, while Li Ruiyan is good at playing piano but not at dancing.

2) I'm good at dancing but not at playing piano. while Li Ruiyan does well the other way around.

反之亦然：恰恰相反。

i am good at dancing,but i can't play the Li Ruoyan is good at playing the panio and can't dance

I am good at dancing,poor in playing the piano,while li ruoyan does well in playing the piano,not good at dancing