Duration of Events

How would one express the duration of a continual event in Latin?

Essentially, what is the Latin equivalent of the French "J'étudie le français depuis cinq ans." or the English "I have been studying French for five years."

Also, are there other constructions for actions that have been completed entirely in the past (e.g. French "J'ai étudié le français pendant cinq ans.") or the future (e.g. French "J'étudierai le français pendant cinq ans.")?

I apologize for...

Duration of Events