How to make the transition of being a rock/Metal Guitarist to getting into playing Death Metal riffs and being a Death Metal Guitarist? I would love to play Suffocation and Morbid Angel songs. Just thought to ask for opinions and advises, would appreciate all the advise.

Thank You.

Not much else to tell you other than learn how to play those songs. That's what I did. A big part of me learning how to play guitar was teaching myself how to play songs like Immortal Rites, Chapel of Ghouls, etc... Chapel of Ghouls is probably the easiest, as it's all power chords... Immortal Rites is a bit more difficult, so there's that. Just practice your tremolo picking and your picking hand stamina, and get good at finger dexterity/strength on your fretting hand. These are all things you'll need.

This'll sound funny but playing games like Quake III helps me write death metal riffs. Because if you've ever played it you'd know it's fast paced and challenging. I use my right hand for picking and left hand for fretting, so when playing PC games like Quake III I'm using my right hand for aiming/shooting and my left hand for movement. It's kind of similar to playing, in terms of how you maneuver your character, so it's like practicing your hand-eye coordination and helping you build up finger/wrist strength and things.

When it comes to leads, I've found that you really just have to feel 'em out in the moment, whatever sounds right.

What he said: listen to death metal, learn death metal songs. If you find a technique in a song that you have trouble with, you can do some focused practice on that technique. There's no tricks, just hard work.

Join a band if you can, that's always been the #1 motivation for me to improve my skills.

Perhaps learn to play some thrash metal songs before (Ex: old Slayer, megadeth)
and then old death metal (Early death, Autopsy etc), then newer death metal songs?