how i will take take of my tip because i heard a lot of people that destroy the tip all what i know is when you finish leave some lead on it so it doesn't get corroded ?
I try to find the lowest temp setting that works well for w/e I'm doing. As much for efficiency as for tip life. The lower you can set your temp, the longer it will stay wet without cleaning. I also leave solder on the tip when I'm done.
also how can i know the original tip from the fake one ?
Hakko tips comes individually packaged in transparent sealed plastic sleeves that you have to rip open (not unlike surgical equipment). If you buy a set of 7 tips for 14.99, they're probably fake.

There's nothing wrong with that, especially if you're just putting together your bench. Especially if you are "practicing," it might be nice to have a variety to try out.