Is there monotize/royalty fee?

I’m new and heard about this few years back but never picked it up till now. Was wondering if there’s anything to pay for the developers after making a certain amount selling my games. For example, unity, unreal etc…

No, Gdevelop is an open source project, so it is “special” in this regard. You will not owe any kind of royalty or special terms to release your game.

On the other hand, it’s not suitable for exactly the same tasks as Unity or Unreal. Gdevelop is for 2D games, and probably best when used to develop HTML 5 (Browser) and Android games. It doesn’t come with any special effects (particles for Web/Android, shaders) yet, but on the other hand it is absolutely free, and easy to use.

The main advantage of Gdevelop is that it could be easier to learn, if you didn’t do any (or small amount) of programming before. With Unity and Unreal it’s still possible, but might take more time to grasp some concepts properly. It might be better to start with an engine like Gdevelop.