I saw that ~ ~하는 걸 봤어요 But 봤어요 means literally you Saw/Looked and this is not how Korean people say it for your sentence. I thought that you want to learn English. ~다고 생각했어요. 너가 영어를 공부하고 싶어한다고 생각했어요. I knew that you want to learn English ~을 알고 있었어요. 너가 영어를 공부하고 싶은 것을 알고 있었어요.