"We were following him for five months."
Translation:Lo seguivamo da cinque mesi.
You are correct... I believe that there are two ways to translate 'for' into Italian. 1. DA The action was in the past and is ongoing . We have been together for two years. Siamo insieme da due anni...In this case the present tense is often used.
- PER. The action in the past has finished. We lived together for two years... Abbiamo vissuto insieme per due anni. 2a. PER An action about to take place in the near future... We will stay in Rome for one week. ..Resterò a Roma per una settimana.
Rule from Da Capo: The indicativo presente accompanied by da + a time expression indicates an action or state that began in the past and continues in the present; it indicates for how long or since when something has been going on. (Da) expresses both for and since. English uses the present perfect tense (I have worked, I have been working) to express this idea.
Da quanto tempo lavori? + How long have you been working?
Lavoro da due mesi. = I have been working two months.
Da quanto tempo conosci Laura? = How long have you know Laura?
Conosco Laura da un anno. = I have known Laura for a year.
Da quanto tempo non andate in ferie? = How long has it been since you have not taken a vacation?
Non andiamo in ferie dal 2015. = We have not taken a vacation since 2015.