(Some addition) - If you see "-ся" on the end of the verb it means "себя", "self". And this also mark a passive: "радовать" (somebody) - active; "радоваться" - passive

They all in passive: things can't buy or sell itselves ;))) - as the movies can not make the movie

I see all these verbs as passive, but it is also possible to see the verbs in the first sentence as reflexive verbs, because the actor is not named ("they sell themselves"). The actor in the second auestion is known (режиссер) and maybe this is why your book says the verb is in the passive voice. The passive voice and reflexive verbs used to create it make it really very complicated. I hope it helps...

yes , here is passive voice of verbs, because- movie is made by -- фильм снимается кем-то- it shows that action is made under the subject of this sentence -movie ( by a famous producer) if it would be - известный режисер снимает фильм - it would show that a producer makes movie- subject ( producer ) makes this action himself , but not under him Не знаю как получилось обяснить , но старался.

The both sentences are passive. If the first sentence were active, it would sound so: Все фильмы покупают и продают (But movies can't buy or sell). The second is also passive, because the movie is shot by the famous director.