Two native speakers were talking. One of them said, "אני יכול לספר לך משהו?" The other replied, "כן, אם תרצה" (I think the last word is pronounced tirtse)
If he meant "Yes, if you want." shouldn't it have been "כן, אם אתה רוצה"?
Note that in English "if" is never followed by a verb in the future tense, although semantically it may refer to a future action. So "if you want" may mean either אם אתה רוצה or אם תרצה in Hebrew.