All the controls seem OK apart from walk which seems to be at a crawl space. I've had this game running a number of times over the years so I'm sure it's not "me" :)

Check your user bindings. They got changed recently since the release of NewDark, which means they will also be different in the GOG release.

easy, don't use it! :D

It's really not necessary

Upgrade agility?

Keep in mind that there's both a run and a walk function, so if you're using Walk it will feel pretty slow.

I'm plagued with the same issue, I walk at a snail pace. Moving backwards and strafing are alright and if I press shift I go even SLOWER if that is ever possible.

Bind W to "Run Forward," not "Walk Forward." Run by default. Hold shift to walk.

And, an fov of 110 to 120 will make it feel a lot faster also.

I change the settings so that up is run but now I move forward faster than left / right / backwards and it feels a bit odd. Plus I kind of like moving through the game walking where possible as it intensifies the tense atmosphere!

Bind speed modifier to Shift instead of walk to Shift+walk. When you hold down Shift, as the speed modifier, it is a bit faster than walk, it is more the speed you would expect.