Translation of Dreiecksverhältnis

One of the most difficult problems I have (and I am sure that others have it too) is getting used to the superficiality of the life in the US. To be superficial means to me not to be able to recognize.
Sunday is fine. Please let us talk tomorrow to arrange a schedule of that day. I will call you tomorrow, but in any case, here is my number again. We could do it also on Monday next week, if it fits everybody.
Sorry for bothering you with so many questions. You are going to be my first online language course. The more I trust you and your website, the more I will use it and recommend it...No problem...