[Mr Kidnapper]

He's full of it. He doesn't understand legal terms.
Royalties are a fee paid in licensing—that is when you've been given permission to use their product or an asset of their product in yours, and you pay a percentage of your sales to them like a tax.
They cannot give you "thousands of fines" or any fines at all. They can sue you, and the government will give you one fine. That fine may be in thousands or millions though. This is assuming that what you were doing is illegal. It isn't.
A registered trademark is the idea that the government will punish people when they try to use your product's name in anything. For example, Harry Potter is a trademark therefore no one but the publishing company that produces Harry Potter can authorize a game called "Harry Potter", or any character within the series of books.
A copyright is a right immediately given to you once your idea has been published. Posting the idea on the internet is also a form of publishing. It is the idea that no one can legally copy and distribute your works without your permission, and you hold it for as long as you live +~70 years. Permission can mean a lot of things. ZUN, for example is extremely relaxed and has given people permission to use everything that he makes so long as you credit him as the original author. It's probably the reason for his success.

Now, I have no idea how a GTA-Minecraft game would work, but it's fine as long as you don't use their names or assets in anything except your own speech, "I thought I'd create a game that was like GTA and Minecraft." If everything in the game can be proven to be made by you and your team, then you're OK as I said in the last post.