Okay well i want to start making 3D games I have basic knowledge on how it all works but anyway i want to make a simple map editor like this https://www.youtube.com/watch?v=Qc8eagCJ8yA where would i start, also i want to make it in Libgdx
That is not a simple map editor.
Okay maybe not but what i am trying to say here is i want to make something like that but all in cubes where would i start?
You make a lot of these topics , if you have basic experience the first thing you should know to do is setup the display and rendering methods. If you don’t know where to start then you can’t possibly know where to go once you finish with one feature. This editor would be way way too complex for just simple experience it has a lot of advanced features that you and even I couldnt replicate. Make something simple , build it into your code.