If its a Circle ... if i want A, and it shows me E (i dont know if this is possible), how can i know if i have to tighten ou loosen the string? As a circle it seen that i can go clockwise (tighten it) or counterclockwise (loosen it). Am i losing something?
You are right, because it is a circle, you can tighten the string or loosen it to get to a note.
So in that situation, you would listen to the A, and see if it is higher or lower in pitch than the E that you want. If it sounds higher than the E you want, loosen the string, if it sounds too low, tighten the string.
If you don't know what it should sound like, compare it to the strings in Justin's video.
http://justinguitar.com/en/BC-109-TuneYourGuitar.phpps: perhaps its not quite possible to get an E when im playing the string A?
Yes, any string can tuned to any note, but this is the most common way to tune it. That is why the A string is called the A string, not because it HAS to be A, but because it usually is.
I read somewhere that you should always tune UP to the correct sound. So..if you need to tune down.. just go DOWN DOWN DOWN... and then UP to the pitch. Is it right?!
That's right too

Always tune the string until it is too low, and then tune it up to the note you want. This stops the string slipping whilst you're playing, which would make it out of tune again. (I'm pretty sure that's the reason anyway).
And your English is great
