how do you create name tags above the head just like in The Killer also how do you make there body morph when they join the server?
You can use the classic way, or billboard GUIs.
Classic way would be to have a model that contains a part called 'Head' and humanoid object and the name of model will appear above the part named 'Head'.
Using billboard GUIs is bit more messy, so just play around with them yourself. There isn't much to them, but they can get annoying to set up how you want them to be.