I left out a few more things and a short translation. Can you please check them, too?
1) Four of your students have sent email so far. Can you please send me the individual email addresses of your partecipating students so that we can start the email partnership? My students can't wait to start it.
2) It has been a week since I sent you my email but, unfortunately, I haven't received a reply from you yet.
3) I'm awaiting the updating (revision) of my balance (accounted) discounted of 5% as you stated in your last email.
4) For this reason, I have fallen behind with the payment of a deposit of 400 Euro for each of my two children as a confirmation of their enrolment in your summer course. I really don't want to miss the opportunity of sending my children to ...... I'm looking forward to receiving your prompt reply.
1. participating
2. comma before "but" - not after
3. I'm awaiting the correction of my balance, discounted by 5% as you stated in your last email.
4. OK