GLFW whit my own graphical system

Hello, for my project I need this question answered : How to send data to a GLFW surface to then be displayed ?

You use either OpenGL or Vulkan. OpenGL is easier.

There are a number of tutorials online, if you search for “GLFW OpenGL Tutorial” you should find some.

I tryed but there is so much functions to learn I prefer making everything myself. So its either I know how the surface work or I need to use wingdi.h

You must use with OpenGL or Vulkan with GLFW. You can use either of these to create a surface and then read/write to that with the CPU, but this will be inefficient compared to using the GPU. A slightly better alternative is to write to a texture with the CPU and then draw that to the surface, but this is still far less efficient than using the GPU.

If you are just want to draw 2D shapes you might want to look at a library like Dear ImGui or NanoVG.

Ok so I won’t use glfw then vulkan is too hard and gl is too slow and still hard

OpenGL is not ‘too slow’, and it remains a decent choice for a beginner. It will certainly be higher performance than drawing with the CPU except under very specific circumstances.