Verb conjugation of "guarantee" in English

I have been living in Holland for the last 14 years and I know the mentality very well. Holland is a small country, everybody knows everybody, so if we want to succeed, we must seize the opportunity.
Thank you for your email! A little question about yourself. How old are you? I think the Americans are using the word color and not colour, but I understand if you are not sure about it.
I apologize that I have not written for such a long time! Please call me on my new phone number, that would be great! How is your son feeling, has he been recovering? I am sure that he will be fine.