In Italian, to express an action that began in the past and is still going on in the present, use the verb in the present tense + da + length of time. This construction does not exist in English, where you would use the present perfect tense. Here are a few examples:
Leggo questo libro da una settimana. (I've been reading this book for a week.)
Prendiamo lezioni di italiano da molti mesi. (We've been taking Italian lessons for many months.)
To ask how long something has been going on, use da quanto tempo + present-tense verb:
Da quanto tempo leggi questa rivista? (How long have you been reading this magazine?)
Leggo questa rivista da molto tempo. (I've been reading this magazine for a long time.)
