I finished my studies and then I have become/became a teacher.
Another post regarding present perfect. Is it sufficient to use just past simple in the sentence above? Let's say that I am talking about events that happened a few years ago but I am still a teacher. I tend to apply here the rule related to present perfect that asserts that this structure is used "to indicate that a state of affair prevailed throughout some interval stretching from the past to present".
Best Answer
It's perfectly OK to follow the past tense, finished, with either past or present perfect in speaking of your subsequently becoming a teacher; but you have to make up your mind whether you are talking about what happened in the past or about where you are now.
If you use then (or next or after that or in 2007) you are speaking of the past event and must use became. Use this if you are building a narrative, describing a sequence of events—which may eventually lead to the present, but doesn't have to.
If you use the present perfect you are speaking about your present status; you cannot use then because you are speaking about now. (You may, however, say since then.) Use this if your discourse is finished with speaking about past events and will now focus on the present.