I want to learn how to type faster. How to achieve this?

Question

Keyboard

No, this is not my first time at the computer. I type faster than anyone I know (70-80 words per minute, 600+ characters). I have never studied typing specifically, I write in three languages ​​without looking at the keyboard, of course, for many years. I type with all ten fingers, but with varying degrees of success.
The problem is that I type >70% of the characters with my index fingers, which reduces the speed of typing. That is, I slide my hands over the keyboard. For example, I always type the letter "X" with my index finger, although it would be necessary with the little finger of my right hand.
What to do? How to relearn? Advise a program, methods, all that.

Answer 1

600 characters - decent speed, if so - why retrain?
and so - stamina and verseq

Answer 2

I also print, it does not soar for me (I can also do around 600 characters per minute, maybe more if the thought is rushing). At least I will start to suffer from tunnel syndrome later =)
According to the subject - clavogons.