1) Focus on timing. You can do this either by looping sections while playing along to a click or with Matt in the tab player. But note, he does use rubato – especially for the 3rd melody. So if you use the player, you may want to put it into synthetic mode.
2) Pause your video at 53 seconds. You’ll notice you are hugging the neck, which limits mobility/dexterity of the left hand. Take a look at this lesson on proper left hand form. Try not to curve your wrist inwards either.