How do you make this kind of gfx?

So i am wondering on How people make the gfx like they have background do they make the rigs then render them and basicly the background is screenshot?

Example Tapping Legends - Roblox

This game’s logo i am not fan of that kind of games but i wanna know how did they make this gfx

It depends, there are gfx artists that uses pictures for their backgrounds while there are some that actually renders their background. The buildings and terrains that you see in the link is built and rendered.

Get a player rig for blender so you can pose it.
Import the character, or create a character in Roblox studio that you want to make a gfx of. Right click on the character and click export.
Delete everything but the hats, then export the character again into a different folder so the textures don’t mess up.
You may want to export the accessories separately because sometimes them being all attached can be frustrating ands you have more flexibility if they’re all separate. Make sure you’re in pose mode and then you can move limbs. You can either make the scene transparent and add backgrounds externally, (like in photoshop or paint.net) or you can add the background right in blender.
To change the rig texture, click on the torso and then go to shader editor. Choose a texture from the folder where you exported the character, if there are a few texture it may take a few tries to find out which one is the right one.
To import objects, to to File > Import > wavefront (.obj) then find the object and the texture should import automatically.

So i use photoshop and blender 2.79 my main question was How they make the background because i am rendering rigs too for my commission logos it was interesting for me to see how they make their backgrounds that good

Looking at it I suggest not using paint v3 or alex’s rig

Ultamite rig is good because it has lots of body meshes

Sorry I didn’t really read your question properly. For background, you could build it in blender or export a background from studio and work accordingly, you could even export items made in studio one by one, but you cannot export materials from studio into blender unfortunately.