Need help understanding

I haven’t had the time to search through the forum to see if someone’s asked this before. If someone has asked I apologise!

I’ve developed a game previously but not using unreal engine (it was a simple basic game) but the few fans I have asked if I could make a better game!

My question is, with the textures and content on the marketplace, do I need permission to add to my game? I’d obviously give recognition to anyone’s products I’ve used! But like the free things from the marketplace, can I use them in a game that I’m intending to sell?

I know this may seem like a very stupid question but I just don’t want to get caught up in a legality issue.
Thank you in advance for the help

All Marketplace Content that you own, including the free assets that are available every month, can be used in any of your games/projects as long as you don’t resell the assets on their own.
You also don’t need to credit the creators of those assets (but still nice to do).

You can find more information in the Marketplace Guidelines: Marketplace Guidelines - Unreal Engine

So you probably don’t have to worry about legal issues when using stuff from the Unreal Engine Marketplace in your game. But there are still some exceptions to those guidelines, but that will be marked somewhere.
The newest (and biggest) example of this would be the Quixel Megascans Library. You can use those assets however you want, but ONLY while you use them with the Unreal Engine, usage in other engines is not allowed.

Thank you so much! That helped a lot!