I found this sentence and I cannot understand the construction of it. I hope someone here can explain to me the different building blocks in it.
”estamos à sua espera a partir das 12h00”
I think the meaning is something like:
”we are waiting for you to go from 12h00”
@zeffi, yes, the meaning is “We are waiting for you from 12:00”. The phrase “a partir de” means “from” (not to be confused with the verb “partir” used on its own) 
As a complete beginner is it also acceptable to say “Esperamos por voce a partir de 12.00?
@d.j.mcdonald53 You can say “Esperamos por si a partir das 12:00” Você as a tonic pronoun is more typical of Brazilian Portuguese; in Portugal, we prefer si.