He has both involvement in the Chelsea goals, They don't happen if he isn't doing what he is doing, He forces the mistake due to putting them under pressure and the 2nd Chelsea goal is good link up with TD who has some nice footwork and he's in the right place at the right time.
United first goal is 100% not a foul if you've watched the goal, De Gea completely misses the punch before DCL is even near him.
The second goal is a mistake but that's why you chase the ball down some day it might just go your way, To just label 3 of his goals as "mistakes" on the opponent is very very harsh.