dating, a relationship

I start one.

私は始めます

I start a serious relationship.

私は真剣な交際を始めます

I start a serious relationship at university.

私は大学で真剣な交際を始めます

I start a serious relationship at university before graduating.

私は卒業前に大学で真剣な交際を始めます

I start a serious relationship at university before graduating, introduced by a friend.

私は友達の紹介で卒業前に大学で真剣な交際を始めます