Programming: Which engine should I use? (UE4/SOURCE/UNITY)

[woahwoahwilly]

I am 13 years old, and handling 3 games. One i already now what engine to use, but the other I need to figure out. Which engine should I use for programming? I don't know much on programming (not at all actually) but I know a friend who does know a lot and was willing to help. Games in detail:

Shadows: The big horror game. Play the Horror Campaign with no dangers or jumpscares, or the Darkness campaign, with dangers and jumpscares. Do rituals to clear up haunted places. Engine: Source 2013 (developed with SDK 2013)

TLF: The classic princess-saver in a new light. No power-ups, swords, shields, etc., but rather heavily parkour based. Survive zombies, gather items, and try to claim back five stolen valuables in the process without getting murdered. The year is 2017, and it's a city near the castle that you have to explore, plus a suburb, and the castle.

 

[photonboy]

My best guess would be to find Unity beginners guides that walk through a specific, simple game.
https://unity3d.com/learn

There are lots of other links to things like this too: https://skillcrush.com/2017/04/03/free-coding-games/

Find the most simple game possible. It's generally best to learn while doing but don't bite off more than you can chew.