Learn Italian: Faccio finta di dormire quando entra. - I pretend to sleep when he comes in.

The phrase fare finta di describes the real-world action of faking something, so it uses standard tenses. The imperfetto ludico is used to set up a shared imaginary scenario, like children playing make-believe (e.g., Facciamo che io dormivo... - Let's pretend I was sleeping...). Here, you are actually deceiving someone in reality, not establishing a mutual roleplay.

Could I use the verb fingere instead of fare finta here?

Yes, you could say Fingo di dormire quando entra. Both mean the exact same thing, but fare finta di is very common in everyday spoken Italian, while fingere sounds just a tiny bit more formal or literary.

Why do we use the preposition di before dormire?

In Italian, nouns related to ideas, attempts, or pretenses often link to a following infinitive verb using di. Since finta is a noun (a pretense or fake), the fixed construction fare finta requires di before the next verb. You can think of it as 'making a pretense of sleeping'.

How do we know the translation is 'he comes in' rather than 'she' or 'it'?

We only know this from context. Because Italian routinely drops subject pronouns, entra could technically mean he, she, or even you (formal). Standing alone, this sentence relies entirely on the surrounding conversation to clarify who is entering the room.