Can I upload my PC/PS4 game into Unreal engine and mod it then play back on PC #NEWBIE:

Hi, this is probably a ridiculous question but I had an idea about something I wanted to do with a game I have. IS there a way to upload the game into Unreal Engine and edit that game, then re publish and play? Its the landscape, buildings, whole game world that I want. I have seen people create games using an already published game, modding it and then releasing it with the changes.
Any help would be appreciated.

What you have seen and what is reality maybe 2 separate things.
What your asking is illegal. Now, if your looking to MOD a current game, assuming the game is a moddable game, you can mod it with whatever engine they used.
Now, if your watching videos of “we made Mario in the kite demo” that’s just tech demos showing off some fun things.

The real question is: the game you “have” is it your own developed game you made, or, just like a game you got via digital download or whatever?
If you own the source, feel free to do whatever you want, and, if you made it in UE, then, sure you can import it. If you made it in another engine, gotta use that, unless you want to recreate it here in UE.
Making a game into a MODDABLE game is more then just “i make mod, yay”. The game has to have the ability to accept mods. More complex then just “making a mod for random game” (example: you cant just mod God of War, it has to have the ability ((ie exposed source in places)) to be modded).