How can I do this?

How can I turn a numeric input into being saved as an app variable ?
I start by saying that I am a completely begginner so I have some trouble rn hahah.

I try to explain myself better, my goal is being able to input a number into the program and I want the program to save that number as a fixed numeric variable.
Then I can used this memorized variable to make functions.

If you just want the value input to be able to be used in other formulas in the app (and don’t need this value to be saved when the app is closed), then simply create the app variable, then in your input field, bind the Value to this app variable. Done.

If by “memorized variable” and “fixed numeric variable” you mean that you want the user’s input value to be saved and then later be available after the app is closed and reopened, then you’ll need to save and load that variable from local storage. If that’s the case, check out this power-up video

Or check out the following: