for refrence, and this is nothing personal because your new, but putting code in format (using the </> at the top of the screen) would make it way better to read 
because right now its really hard, and if you would like faster help that would be your best bet. Yet again absolutely not targetted towards you<3
although, these errors seem to be easy.
‘item’ not being declared means you didnt use an:
@onready var item = (whatever)
at the, preferably because it just makes better sense to put variables there, top of your script. same with ‘file’ (although, im assuming youre trying to call a scene with this. that means you would have to do something like so:
@onready var file = load(#string name here, dragged into the paratheses, should show up looking like a file name, with the paths to the file)
The not found in base self error is because you need to declare a new function like so
func _ready():
pass #whatever it is here
func custom_function():
pass
#whatever you want this to do here and then you need to call it somewhere
I would also provide the name of the video as well so i can help you better.
and, if this is your first project, I would recommend doing a simpler project/tutorial than the one you’re doing right now. Don’t just jump straight into it, i made that mistake and it doesn’t help.
One tutorial that really helped me was How to make a Video Game - Godot Beginner Tutorial by Brackeys (https://youtu.be/LOhfqjmasi0?si=i8rd_q9u-M3WAfqX should be it). Its pretty simple and leads you through all the basics for a 2d game. And its way more beginner friendly than what I see you trying to do right now. Plus, he explains WHY things work, and you need that for all this hard stuff. Obviously there could be better tutorials for your learning style, this is just the one i learned before fully diving into godot.
Hope that helped 
