Surfing Waves

I have been surfing for a while now and already know how to turn the board left or right on a wave. The problem and question i have know is how to go down the line on a wave. I know asking questions online isn't really a good idea but i really wanted some advice on this . When i catch a wave my rides are usually short and idk if im going to slow or what the problem is ?

You really just have to feel it, and it takes time. If you are riding a fast wave that requires speed to make sections try to stay on the top third of the wave, and as your board starts to fall down the face pump your board back up the face and down the line for speed. It is hard to explain, and the best way to get good at it is to surf more! Have fun!