You need to practice with a metronome. Learn something you can actually play too or you won't really be learning anything. You seem to be aiming a bit high at the moment. No offense you just are. Learn something easy, learn chords and scales and theory, and if you like metal then play scales constantly. Don't ignore everything else but concentrate on scales and building dexterity and speed.
The best way to do this is to practice four to seven hours a day or more (haha). Actually it probably is but you shouldn't need to if your in it for the long haul.
I would (and did) start by learning all the postions of the pentatonic scale and then practice playing through it for hours (honestly just play through scales to a metronome for hours and hours and hours).
You should start writing songs though, if there is one thing I wish I had done is start actually writing and recording as soon as possible. Being a good song writer is infinitely more important than being abe to shred the fret board. Technique is just the tool and the better you are the more tools you have to play with when writing but being good at writing is more important.
I should add by saying that just knowing how to play scales is not going to make you a good guitarist. I mean I think it is important to build up your profiecency with the instrument and be a technically sound player, but keep in mind that your still trying to become a musician (I should think any way) and you are gonna have to play music to do that and music is not shredding and it's not scales and theory. Honestly I started out focusing souly on those things and I think I am well off for it but I also had to figure out that there was a lot more to everything than just playing fast and well.
The main thing is don't try to rush it. Practice hard and learn a lot and it will all come in time.
But yeah like everyone else said and I said early stop trying to play songs you can't cause you aren't really learning anything. Until you can play it (perfectly) don't try to play it to speed.
Use a metronome and build up. If you keep at it you'll get there eventually.