Translation of unzulässig

I have contacted you 12 months ago to propose your school's inclusion in our language school directory. I wanted to inform you that our site achieved high positions in search engines last month.
The easiest way of writing sentences in Spanish and English is to communicate with other people by email or by chat. I found the different time forms quite in Spanish very confusing at the beginning and it was the most difficult part.
If you want we can exchange our phone numbers, then we can communicate better. I can then correct your German pronunciation, and you can do the same for my Spanish. What do you think?