itch.io

I would recommend asking GB Patch before you make another game with similar things to their games, just to be safe, but they have mentioned before they use the Ren'py engine. Pretty much every visual novel uses it because it's pretty easy to learn and works well, it does use some python language for the code but for the scripts it's easy to learn. First obviously you write the actual script, but for the choices changing future thoughts and dialogue I'm pretty sure you set it so when they make a choice it gives the player a thing (or adds to it so it only gives it after they select enough of one kind of choice or whatever) and when it gets to a part where the dialogue would be different depending on their previous choice(s) it checks if they have the thing and if they do then it gives them the matching dialogue for it. 

Im sure my explanation isnt the best but I recommend first learning Python and Ren'py! I will say for any game even close to the scale of Our Life you'll probably want a team because of just how many words and code you'll need to get even a semi-long game that has the kind of dialogue variety that Our Life does (even just one step has at least a million words total if I remember correctly)