My students often make mistakes when they talk about the cinema or the theatre. The first concerns the theatre. If we go to the theatre, we see a play, not a ‘theatre play’. It sounds strange adding the extra word, similar to when students say ‘chicken meat’, when they only need to say ‘chicken’.
The other thing is about what the actors do. In English, the actors ‘act’, they do not ‘play’. You can say that are playing a role or character, but generally they act in a film or a play.
So, let’s put them together:
Brad Pitt is acting in a new film about aliens. He is playing the role of an alien killer.