Accuracy before speed
Fast typing with lots of mistakes ends up slower than steady typing, because you spend time fixing errors. Aim for accuracy first. Speed comes as your fingers learn their positions.
How to practise
Use a slow pace and aim to type whole words with no mistakes. Raise the pace only when you can do that comfortably. In Zomtype, start on Practice or Relaxed: every word you type without a single mistake earns a bonus, and the end of each run tells you how many of your words were flawless.
See also: How to type faster, A two-week beginner plan.