The error message is pretty clear:
no suitable method found to override
And since you specify the line as:
Console.WriteLine(weapon1.ammo);
I'd guess that you started out with a blank file, and just added that code - so you are missing a
using
statement:
using System;
Or you have not got the required references in your project.
If it's not clear from that, go back to where you got the tutorial video, and ask there. Chances are this is a YouTube jobbie, and frankly, they are nearly all total garbage produced by people who have no idea how to make a video, and no real idea what they are doing with the code either ...
Asking them is a good way to find out: if they reply with useful information, then they might be taking it seriously and know what they are doing. If they don't (and most won't because they can't) then you are there for the views and to get subscriptions. Go elsewhere.