I specialize in the Godot Game Engine 4.
Godot is a free opensource game engine which is becoming more and more popular.
The engine is constantly developed by the community, and in its current version is graphically comparable to the Unreal Engine 3.
The engine can be used by everyone.
More information and the download link can be found on the Godot website: https://godotengine.org/
I am also working with FlaxEngine, Unigine and Unreal Engine.