Idiom
on good sideon (someone's) good side
in a situation in which someone is pleased with you.It's a good idea to get on your manager's good side when you start a new job.
Usage notes: the opposite meaning is expressed by on someone's bad side - in a situation in which someone is angry or annoyed with you:
You don't want get on her bad side – she can be really mean to people she doesn't like.