We were in college together.

We went to the same college.

We went to the same university. (на английском college и university - это часто одно и то же)

- Where did you meet Derek? / Где ты познакомился с Дереком?

- We were in college together. / Мы вместе учились в университете.

I'm in forth grade.

- What grade are you in? / В каком ты классе?

- I'm in forth grade. / Я учусь в четвертом классе.

I'm studying just for the hell of it.

I'm studying just because I like it.