Don’t ever bother trying to learn how to play fast. Really, don’t do it. Good technique is about accurate fingering and hitting the right notes every time, especially when it comes to scales and playing tricky bar chords. Concentrate on precise fingering. The truth is, learn to play properly and speed will happen all by itself. The biggest obstacle to fast playing is poor technique. Learn good technique and fast fingering will be a chucked-in-for-free bonus. Always take your time and play slowly.