ESTEEMED SPIRITS OF the oven

Brigth ones who have dwelt before on this earth, I attach to your broad knowledge and ask: WILL YOU ASNWER ME?
I call your names so you can show me the source, that you before me have found, so I too can drink from it riches
Of course, the GOLD SOURCE!

For with it I can surely make my own Counter Strike? I have searched but not found, a counterpart to the Source SDK.
So that I can make my own mod, or even a stand-alone game.

Is there any here who can hint the next step I should take?

You can't make a standalone game, since Valve doesn't licence GoldSRC to anybody these days, but you can make a mod with the Half-Life SDK. I'd say Half-Life Updated SDK is a good place to start:
https://github.com/Solokiller/halflife-updated

For HL SDK programming knowledge, definitely start here:
Half-Life Programming - Getting Started

For mapping and other tomfoolery, check out the Tools and Resources page. J.A.C.K., WadMaker, SpriteMaker, GIMP, Audacity are all you need to start modding GoldSRC in general.

YOU are a bro!
THerefore, thank you