Starting a Survival 2D Game, looking for advice

Greetings !

I'm a high-school student and for my project i have decided to make a game. I want to make a 2D game that's played from bird's eye view. It would be kinda a survival game where player crashes into an island with plane, there he will gather materials, craft items, kill mobs, explore caves and so on, and the way this game ends is that he has to build a ship so he can escape the island or something like that. I have some experience with Qt i have gone through some tutorials and so on and i still feel like i'm lacking knowledge on how to make a game like this, when i ask myself okay, caves, how will i implement caves and mobs inside them and so on, i feel lost and nervous. So if anyone knows anything else from where i could learn more about creating a game like this or anything that has to do with making games in Qt, please please let me know.

And i'm sorry if my English is not as good, i hope you understood most of it :3