Oh FFS, just because the kid's foreign and hasn't hit form yet doesn't mean he's struggling with the pace of the league. If you transplanted Gisdol's Hoffenheim to England, they would be considered one of the most frenetic, attacking teams in the league, and they were playing against sides like Bayern, Klopp's Dortmund and Schmidt's Leverkusen (i.e., not exactly lethargic with the pressing).
What Firmino is struggling with is receiving the ball squeezed against the right flank with 8 opposition players and virtually zero support ahead of him. In other words, it's the general lethargy and incoherence of our build-up play. At Hoffenheim, he stayed forward in a counterattacking side that brought the ball to his feet quickly when there was 360 degrees of space to work with. Unless we do the same, he's going to have to add a whole new dimension to his game which will take time he's probably not going to be given in the current atmosphere.