The first bar of this is played legato: pick the first note, 11th fret held down with index finger; hammer on 12th fret with middle finger; then hammer on 14th with ring or pinkie. Repeat on next string. The pick on 11th, hammer 13th.
The second bar is just a case of slowly increasing speed using a metronome. Start at a comfortable speed, then increase by 2 BPM, then decrease by 1, then increase by 2, decrease by 1, and so on. That's the method promoted by Anders which I've tried with success (although I tend to use higher increments).
Good luck with this. It's damn fast
I wish this forum had a "block user" feature. Possibly I'm not the only one......