I will try to help you but be warned, I might go on forever.
First, let me say that speed is not an end all be all. Those here who know can attest, one of the best pulls in the game had mediocre speed at best. His ability to read a defense and and wait one out was unmatched. He would hit holes that simply were not there. He is at least a 13 time world champ. Steve Murray. Never had a fast stroke but he did have the gift of finding the hole.
Okay, now, hitting the ball hard is not necessary to score. Let me state, ANY ENERGY WHICH IS NOT DIRECTED AT LATERAL MOVEMENT OF THE ROD WILL SLOW THE MOVEMENT OF SAID ROD. Let me explain. If you try to hit the ball excessively hard, your body moves for balance compensation, your elbow moves either too far out or in to generate the power for the ball to go forward, the man comes too far off the ball to hit it which gives your opponent a clue where you will hit it, also the death grip on the handle is also detrimental to the stroke. What you want is for all energy exerted to be parallel or tangent to the rod you are shooting on. Even though I have not seen you shoot, I will almost guarantee you have a lot of unnecessary body movement when you shoot the ball.
The fix. DISTANCE. With your arms extended, approach the table until your palms touch the table. This will be your approximate distance of your right foot from the table. Another way to do this is to pull the three rod completely out and with your right hip, make a parallel line to the table. Don't worry, it's gonna feel weird at first, believe me, you are not to far from the table. The reason for this is balance. Whether you shoot a straight or a long, you must have balance throughout the entire stroke. Have good balance and you eliminate body movement, Less body movement equals more speed in the stroke.
Next, the GRIP. With the man either perpendicular to the table or just slightly angled back, grip the handle as if you are about to shake it's hand. Now try to put your thumb on top of the handle. If you can without any strain, you have the right grip, if not, rotate hand accordingly. Also, use a very loose grip at the beginning of the stroke vs. a tight one. What this does is eliminate backswing. Eliminate backswing, add speed to the stroke.
Now, STANCE. If you have done so far what I've said, you should be standing with shoulders square to the table. With your back foot still in place, turn your body 45 degrees and square your shoulders to the corner of the table being careful to leave your feet at least a shoulder width apart to keep your balance. What this does is put your body in perfect balance for the finish portion of the stroke before it starts vs. trying to move your body there in the middle of the stroke. Your stance however, will be something you have to experiment with because of different bodytypes but the two constants are distance and balance. This conserves a lot of energy which again adds to the speed of the stroke.
STROKE. There are basically two different strokes with another being a combo of the two. The most accurate is the square or the "7" stroke or what I sometimes call the "punch" stroke and is also referred to as the "dead stroke". This stroke is called this because the finish portion of the stroke is back towards the other side of the table which generates the forward and sometimes angled back path of the ball. The other is called a spray stroke which is primarily a speed stroke. The finish of this stroke is towards the wall in which you are shooting. Since the ball never squares or angles back, the release of the ball is that much quicker. The last is a combination of the two and is what a lot of the pros use. The combo of the 7 stroke with a little spray allows you to get to specific holes with speed.
Hopefully I have not bored you to death. Before you start worrying about speed, concentrate on TECHNIQUE. That will get you farther than just pure speed.
As far as what you should learn, BALL CONTROL BALL CONTROL BALL CONTROL BALL CONTROL.
ICEMAN.