Verb conjugation of "adulterate" in English

It would be an advantage if you could send it via DHL, UPS or another Currier, because the parcel was lost once when we sent it with regular mail. Please send me a reference number after you send it.
Yes, my Spanish is much better than your German, but it is not true that I do not want to learn with you. I think this is not an issue. Where do you come from in the U.S.? East or West coast?
Which region in Germany are you from? I live in Aarau in the state of Argau, that is in the middle of Switzerland not far from Zurich, Lake Zurich and near the border city of Basel.