Hey, Ive been playing on and off for a while not realy learning anything....

now I wanna pratice more and Improve fast, I can play many houres a day.

I basicly wanna play Hardcore,Post-hardcore, Deathcore stuff And I would Like to know what would be the basics, or techniques that could help me improve towards this goal.

I mostly wanna learn rhytms rather then leads.

So, any help?
hammer-ons, pull-offs, alternate picking, tapping etc.

IMO You should focus on alternate picking for now.
Agree with maddmann, alternate picking is the technique you´ll need most, followed by some legato i believe.
Easy stuff for alternate picking is takeing scales and play through them.
But i prefer doing this quote i´ve said to my friends that play guitar when they ask me what i practice: "I practice what is hard for me"

If you practice something easy it wont have much effect, take some riffs from a deathcore song you like and use them for practice. Anything helps if you practice riffs slow at start and speed up when you can play it PERFECTLY.
It may also be good to learn some sweep picking, I don't really listen to much deathcore - but I know it is useful for various type's of metal. If your interested in creating your own sweeps, you may also want to learn how to create an arpeggio (in it's various forms: minor, major, augmented, diminished) start learning how to use scales as a reference to create your own music.
I have basic knowledge of scales as im a piano-synth player.

I just dont know em on guitars.

I tried doing a bit of sweeping , and even slowly its very hard.