I can't change the shaders at all

I want to disable the shaders, but when I press the Scroll Lock button, it doesn't do anything.

Not only that, but the DoF blur is SO INTENSE that it makes it so difficult to read things on the screen and even blurs out the HUD. I go to the CFG settings to change that but NOTHING HAPPENS!

Basically, I ruined Trackmania United and there is no way to fix it. I'm really pissed.

Hey hey hey. Hold your horses. Nothing's ruined.

1. Even if the toggle key doesn't work you can always disable the effects one by one in the configuration file. It's more work all right, but you can do it.
2. If DOF or any other effect is not to your liking you can fine-tune it yourself, that's what all those settings are for.
3. If you really don't want Reshade at all, you can always remove the files it added in your game folder and everything shall return to normal, no harm done.

Don't be angry...

"even blurs out the HUD"

You can use a feature called "HUD_MASKING". So enable it. Then go to MasterEffect folder. You have file called "mcmask". Take a screenshot of your game. Then go to MasterEffect folder. You have file called "mcmask". Draw new mask for your game. Done.

/Sorry for my poor grammar...