Sorry if i repeating this topic.

Is shred so hard to do?I ask because it's my dream to shred like Yngwie Malmsteen,Ritchie Blackmore,Angus Young and another guitar players,but i only know pentatonic scales and some techniques.I see people shredding at Youtube videos and i Just get down because i can't do it.But i am Just asking that:is possible shred with pentatonic scales?

Learn your scales and practice. Practice as much as you can, and practice with a metronome if you are able to. Shred is hard, and the only secret to it is to practice as much as possible.

Takes years of consistent and methodical practice to shred cleanly. Practicing scales is hella boring too, but you can spice it up by practicing some short, faster lead runs. It's much easier to play fast when you practice a specific string of phrases. Improvised shredding is master level stuff, give it 15 years.

This is pretty much all there is to it. The real difference between who can shred and who can't comes down to the ability to do really boring stuff (precision scale/picking exercises) like they're as fun as playing songs you like. I suggest getting your laptop and finding a metronome online, and then opening another tab to play a YouTube video at a volume low enough to hear the metronome above it. That's a way to make time fly faster while you practice boring stuff. Your proficiency in picking is a product of the time you spend practicing and the seriousness/focus with which you practice.

Doing chromatic and speed endurance exercises also really help too. I also highly recommend the Paul Gilbert instructional video he made in the late 80s, as he goes over a lot of fundamentals that can trip you up starting out if you don't know any better.

and even then, it's not guaranteed that you'll be able to shred like Malmsteen.
You might be able to only reach 16th alternate picking in 140bpm, which is nice but not even close to Malmsteen level.
Everyone has his limit, everyone's brain is wired differently, not everyone will be able to reach this skill level even after years of practicing.

In my opinion, the sacrifice you'll have to do (basically an endless amount of hours from the limited amount of hours you'll have in your lifetime) in order to reach those levels, doesn't worth it.
Nobody really cares about shred anymore, its not the 80's, and even then it was just a trend.

If to shred is your 100% dream, then go for it, but I think you'll want to be a professional session musician (or an artist), you'll see that shred is a nice to have skill but you'll use it maybe in 0.05% of your time on studio/stage.