关于talk的用法

I am talking with my girlfriend
我在和女友讲话.
I am talking to my teacher.
我在跟老师讲话呢。
We are talking about him
我们在讨论他呢

talk to sb.对sb.说话；
talk with sb.与sb.对话；
（意思相近）
I was talking to(with) Marry at that time.
talk about sth.谈论某事
I told Marry about the case at that time.

Our teacher is talking to Lucy.我们的老师正和露西（Lucy）谈话。

We looked around the school and talked with the principal.我们参观了那所学校，并跟校长进行了交谈。

When they get together,all they talk about is football.他们在一起时，谈论的都是足球。