Key Grammatical Phrases including 对，再说，还，要不然，还。。。呢，没有。。。那么， 一。。。就 in Sentence Usage I have a list of sentences with important grammar phrases. I was wondering if someone could check if they were grammatically correct or not.
Thank you very much!

他对数学很感兴趣。
这么早，别去了，再说外面也很冷。
教室里越来越吵，你们要安静一点儿，要不然我会很生气的。
他还没回家。
你是什么时候来的？
妈妈：你为什么还没做功课？
我：因为我还在吃饭呢。
我没有她那么多钱，可是他没有我那么多朋友。
我一到东京就打电话给你。

Again, thank you very much for your time and help!
These sentences look like exactly the ones I hear from people around me and the ones I would use to speak to them, and most important of all, no misunderstanding caused.  There might be minor rhetoric modification but nothing grammatical.  If there is any grammatical flaw, maybe all of us should go back to Grammar 101.