"Tamer has a house."
Translation:عِنْد تامِر بَيْت.
No! It should be when "Tamir" coms at tge beginning of tge sentence So both of this are right عند تامر بيت تامر عنده بيت Just choose whichever you want.
Yes, of course it should ! But most of the speakers at Duolingo do NOT seem to have an idea of what they were about to read. Don't they have the complete sentence in front of them ? Moreover, they speak Arabic NOT the way somebody TEACHING other NON-NATIVE learners of MSA or FuSHaa should do. Here we get a deep realistic dive into the world of Arabic: Pretty much of this and that, to and fro and a bit of nothing and of all.
Be patient and get used to it. Tomorrow, Inshaa2allah, you will better understand.