我练瑜伽有一段时间了。

I've been doing yoga ___for ___some ___time.

我观察你有一段时间了，现在我很清楚，自从你换了工作，你一直工作得太辛苦。

I have been observing you ___for ___some ___time and it's now quite clear to me that you have been working too hard since you changed your job.

她学英语有一段时间了。

She has been studying English ___for ___some ___time.