use after + phrase; use later alone (at the end of a sentence or phrase)
I’ll call you later.我稍后会打电话给你。
I’ll call you after I get home from work.下班回家后我会打电话给你。
First, he bought a new car. Two weeks later, he bought a new motorcycle.首先，他买了一辆新车。两周后，他买了一辆新摩托车。
He bought a new motorcycle two weeks after he bought a new car.他买了一辆新车的两周后买了一辆新摩托车。
You can say ‘later + time period’ to refer to an unspecified time in the future.
I’ll finish the project later this week.我将在本周晚些时候完成这个项目。
We’ll go on vacation later this year.我们今年晚些时候去度假。
Never end a sentence with after. Instead, you can use afterwards.
Did you go home after the baseball game?棒球比赛结束后你回家了吗？
No, we went out for drinks after.不，我们之后出去喝酒了。
No, we went out for drinks afterwards.不，我们之后出去喝酒了。
Where did you go after the movie?电影之后你去哪里了？
Where did you go afterwards?之后你去了哪里？
Use ago to talk about past times in reference to the current moment.
Use before to talk about past times in reference to another moment in the past.
I graduated from college 3 years ago.我3年前大学毕业了。
I met my girlfriend two weeks before I graduated. 我毕业前两周遇见了我的女朋友。