Scripts comaptible with FiveM : https://forum.cfx.re/c/development/releases (there’re a lot)
To make them working, just follow installation section
There’re some tutorials : https://forum.cfx.re/c/development/tutorials
Here a small tutorial for create some basics scripts : [How-To] Create a basic script
You should also look at LUA or C# languages and have a look to http://runtime.fivem.net/doc/reference.html (it’s a list where is stored a lot of functions which can be used on one of your script)
You should also take as example all scripts which are available here to understand how it’s working