"We are not angry with you."
Translation:Nosotros no estamos enojados contigo.
You are correct. The permanent/Temporary thing should not even be taught anymore. I've only seen it done correctly once... and it wasn't on Duo. Use this instead:
SER: DOCTORE (D-date; definition, O -occupation, C-characteristics, T-time, O- origin, R-relationships, E-events
ESTAR: PLACE (P- position, L- location, A-action, C- condition, E-emotions.
Terry, words like contigo are a combination of the preposition con and a prepositional pronoun. Because a preposition is already present the use of another proposition would be incorrect.
con + mí = conmigo (with me)
con + ti = contigo (with you)
and there is actually a 3rd one:
con + sí = consigo (with himself/herself)
Saying 'a contigo' would be like saying 'a con ti'. Two prepositions in a row like that simply doesn't work.
The pronoun 'nosotros' is entirely optional in either case. This is because the verb conjugation can only mean one thing: estamos = we are. Including it simply adds emphasis on the subject. Please report these if you are ever marked wrong for including it or not including it.