How to make stable fast movement and easy movement up ramps, like in Speed Run 4?

First of all, I would like to say I am a beginner scripter, so I apologize for not understanding certain concepts.

I want to make a game similar to Speed Run 4 but have realized that fast walk speed is very unstable. If you play Speed Run 4 then compare it to fast walk speed in a different game, you can see the difference. Fast movement in Speed Run 4 is very smooth and easily controllable. You can also go up ramps smoothly. I am not requesting a script, I am just wondering how they achieved this, and how I can make my own script. I have not tried any scripts due to having no idea how to achieve this.