All your problems are just you making typos. C# is a case-sensitive language.
This line (can’t give you the line numbers as you didn’t post your script using the forum code tags): SurfaceEffector2D.Speed = boostspeed;
Should not be referencing the SurfaceEffector2D class, so it should probably be using the variable you set up: sufaceEffector2D.
Then if you look up SurfaceEffector2D in the Unity scripting documentation (https://docs.unity3d.com/ScriptReference/SurfaceEffector2D.html) you would see that there is no property called Speed. It is called speed
So the line should be: sufaceEffector2D.speed = boostspeed;
That’s because you did not define a variable called SufaceEffector2D, you named the variable sufaceEffector2D.
Therefore this line: SufaceEffector2D.Speed = basespeed;
Should be: sufaceEffector2D.speed = basespeed;
Install Visual Studio Community. The program itself will highlight your errors, your current editor doesn’t (from what I can see it’s probably Visual Studio Code).
Asking for help with compiler errors is like asking someone to hit a nail while holding a hammer yourself.