I have some advice. From my experience, people who speak fast don't worry about mistakes. If you worry too much about speaking mistakes, stop it! :) Practice talking and worry about mistakes later. Just try to talk faster without any other concerns.

The main thing is to keep practicing in a regular basis. If you speak 1-2 hours everyday, you should see some improvements soon! (and if you can do it more than 2 hours, even better).