Distance control is by far the most important part of putting and this practice drill is a fun way to improve by trying to hit successive balls closer to the hole without going past it
Improve your speed control on putts by selecting two different length putts, alternating shots to each one and keeping the shot within the safety zone
Practice your entire swing in super slow motion, this will allow your mind to focus on the correct muscle movements needed instead of trying to make your brain work on the correct movement while you are swinging, just do it don't think it