I am looking for tutorial that can guide me in making this game
These are the features I want in my game
Item colleting
Storage of Items
Pause menu
Save menu
Checkpoints
Monster specific items – Only that item can kill that monster
Magic leveling system
Player Customizability, pick one starting magic and two items
Item leveling system
Type Platformer
You got a great list you want that someone make it for you (maybe someone have the time to explain everything to you, maybe not, who knows) sooo,
I give you some youtube links to watch. May be usefull to you.
Mathew Cornelius videos:
https://www.youtube.com/channel/UCRtgG1FE7yPmw4jgyTWFOzQ/videos
Steven’s Tutorials:
https://www.youtube.com/playlist?list=PLzhCoXduIV_CMSWu85En-C8E4hCiZyaVH
My videos:
https://www.youtube.com/watch?v=GvjWLEz7OeM&list=PLyzdcrVNlfgjZj1WXPg5ouqmJ7Vq-RoCQ
And tutos/examples I have upload to my blog:
[url]Simple tutorials]
And of course look all the examples from Gdevelop example folder!
Maybe you find those links helpful, or maybe not, but you find lot of things on youtube besides of those I give you and of course you can use search option here in forum to find answers 
(Or community work together and first 10 people make 1 per dude 
)
If it’s your first game start with the platformer tutorials and expand that game making it from the quick tutorial into a full sized 1 level game. Then build something from scratch on your own to get a feel for it all. Then expand on what you can do from there by experimenting with different things in the editor.
You can’t download a program and expect to make a master game overnight no matter what the program is. Set out to learn one thing on that list at a time and before you know it you’ll be able to put the game idea you have together