Looking for a quick tip or advice

Hey guys im just starting out on trying to learn some basics with game development before i try to go ahead and actually pay for a course or two, all im doing right now is trying to learn how to make an open world for me to just run around in no interactions with anything just movement, its more the texturing and type of graphics/details for the open world, basically i want it simular to the graphics and details of runescape or fortnite maybe around the same size of the worlds aswell, like i would make the open world in blender then import to unity or ue4 or something for the character movement.

if anyone can help me with this please and thankyou in advance and appreciate it.