We have interest in English .

我们对英语感兴趣。

We have interest in English.

我们对英语兴趣。

We have interest in.......

我们对……很感兴趣。

Because you, I have interest in learning English!

因为你，我有了学习英语的兴趣！

Of course. If you have interest in it, we will begin tomorrow.

当然有新的，如果你有兴趣，明天就可以开始。