They say bonjour for both good morning and good afternoon

Hi! example family you can say: Hi!= Hello! =Salut, Bonjour. It's better to say meet in the street a person you do not know. "Bonjour". It's better to say meet in the street a person you know a friend where number friends. Salut!/Bonjour ! you can say : "hello!" too. / "salut!" , "bonjour" just to think if tonight says: bonne nuit!, bonsoir! bonne fin de soirée!

It is bonjour. Although afternoon translates to après-midi, the expression "bon après-midi" is not used as a greeting. So "bonjour" is correct.

Good Afternoon = Bon après-midi. We use that to wish a good afternoon to someone who leave us and will be back in the evening (for exemple your children who go to school at 01:00 pm and come back at 04:00 pm)

I'm sure you've realized by now, but just a little tip of advice: languages don't always translate word for word, even similar ones like English and French. I had to learn that the hard way and got a lot of wierd faces for it, too. Good luck in your studies :)