fit in           
phrasal verb with fit verb uk/fɪt/ us/fɪt/ -tt-
C1 合得来;适应
to feel that you belong to a particular group and are accepted by that group
  It's no surprise she's leaving - she never really fitted in. 她要离开——这一点也不意外,因为她从来都没有真正融入过。 
 B2 相合;合适
If one thing fits in with another thing, they look pleasant together or are suitable for each other.
  It's a very nice sofa but it doesn't fit in with the rest of the room. 这个沙发很漂亮,但是跟房间里其他的家具不搭配。 
 - More examples
 - She says that she doesn't fit in at her new school.
 - She's exactly the type of person we need in our department - she should fit in perfectly.
 - It became clear very quickly that the new assistant wasn't going to fit in.
 - I tried so hard to fit in, but the other staff there were reluctant to accept me.
 - Being the only father at the mothers-and-toddlers group, he struggled to fit in at first.