Can I use the free marketplace content in a published game legally?

I have recently began to think of creating a game using Unreal Engine 4. This lead me to a few questions. First, I was wondering how profits are given to Epic Games. When you install the engine it is said that 5% of my profits will be given to Epic Games. I as wondering how I am to pay you, whether it be a contract or some other method. Second, on the “Learn” tab of UE4, there is free content made by Epic Games. The three I am interested in are “Landscape Mountains,” “Water Planes,” and the “Open World Demo Collection.” Am I legally allowed to use these content packs for my game and then publish it?

you’re free to use the content from the learn tab, i’ve asked the same question before, you can check it and see the official answer: Legal question - AnswerHub - Unreal Engine Forums

also in the faq
"What can I do with content I obtain from the Marketplace and Learn tab?

Besides using this content for learning, experimenting, and prototyping, you can also ship it in your own products, too! However, you can’t sell or sublicense Marketplace content to other developers for use in their products, e.g. via website or e-commerce mechanism built into a 3D development tool."

about the 5%
i don’t know how exactly, but before shipping your game you have to submit this form: Epic Games Technical Support & Customer Service | Epic Games
so epic will be notified and you will have a way to communicate, and probably they will tell you more specifically how to pay in this step.

Thanks veccher!

glad to help you guys =)