Basically, to avoid making mistakes, you should only use the present participle to describe a situation in which a person is actively doing something in that precise moment.
For example if someone asked you in Italian ‘what’s your Dad up to?’, you could say: ‘lui sta dormendo’ - he is currently sleeping.
If you simply used the normal present tense and said ‘lui dorme’, it could be interpreted as ‘he sleeps’ which gives no indication of when he is sleeping, just that in general, he sleeps.
Another thing to watch out for, is to NOT use the present participle to directly translate from English when speaking in the future tense.
In English, we use the equivalent of the present participle also to express a future action, such as ‘Tomorrow, I am going to the cinema.’
To express this sentence in Italian, you can’t say ‘Domani, sto andando al cinema’, because to say that tomorrow you are currently going to the cinema makes no sense!
Instead you should use the future tense ‘Domani andrò al cinema’ - tomorrow, I will go to the cinema, OR you can also just use the normal present tense: ‘Domani, vado al cinema’ - tomorrow, I go/am going to the cinema.
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