How to create an only group nametag?

Hello, How to make that if a player joins a certain Roblox group he/she has a custom nametag?(Like for example the name of his division)

Since you have provided no code I'll just explain what you'd have to do. I am also going to assume it is a nametag in the 3D world space. You would need to create an event listener for players joining. Then use the 'IsInGroup' function of player with the parameter being the 'GroupId' in the group's URI which is an integer value as a condition for an 'if' statement. In the condition you'd need to add an event listener for the player's character so the nametag will be added to the character every time they load in using the 'CharacterAdded' event of the player.. Then in that condition you'd have to create or clone a 'BillboardGui' with a 'TextLabel' as it's child into the player's 'Head', 'Torso', or 'HumanoidRootPart'. I would suggest having the 'TextScaled' property in the 'TextLabel' in the 'BillboardGui' set to true. Finally, you'd have to change the 'Text' property in the 'TextLabel' in the 'BillboardGui' set to your string.

I would recommend at least attemping to write it and coming here for help next time.