Hi colombiano
Fist off let me welcome you to AFN

it's always great to have new members.
The best way to get advice on a grow is in a grow journal, in you journal you can give us all your specs and equipment you use etc, it helps to give us a clearer idea, what you are growing, how you grow and equipment used.
It would be great if you made an introduction so we can welcome you properly and so you ca meet our wonderful members.
I'm gonna give you a couple of links to get you started.
Introductions

-
https://www.autoflower.org/index.php?forums/introductions.35/
New Growers forum -
https://www.autoflower.org/index.php?forums/new-growers-forum.44/
When reading seed packets they might say seed to weed in 8 weeks, this often refers to plants grown under ideal conditions, often your plants will take a couple more week to reach their full potential.
You can pinch out some of the large fan leaves if they are obscuring light from reaching bud sites, go carefully and don't take too many off ( you can't put them back on once they are off).
A picture, my man is where it is at right now, without pics we are flying blind.
However if you trichomes are mostly milky with some amber, 70% of Pistils(hairs) are golden and your fan leaves are fading then harvest time is upon you.
peace bro
Arty