Anyone who have some advice and know how to play good "blastbeats" that is very popular in deathmetal and grindcore?
As with most any rythm, all the basic rules apply. Practice to a metronome, working your way up, practice consistently and methodically, etc.
Become fluent with your single stroke rolls, first of all. Also become fluent with your double bass drumming because it's pretty much the only way to play a reverse blast beat.
Try to look out for your technique. Don't rely much on rebounds and always be on the lookout for nasty bad habits in your grip (there's a link to a video here on the site showing what NOT to do when playing death metal). Check your posture too as most deathmetal drummers slouch way too much.
I think that is basic when starting working blasts.
pull your shorts up pretty high, having the crotch of your shorts too low on your legs (like with most pants these days) will inhibit your motion.