Unfortunately there aren't any video tutorials (that I am aware of) but I'll do my best to try and explain.

In terms of example projects, the first one that covers the most basic things is the Guided Tour that comes up when you first open Decker. It explains the most basic functionality, and I think that's where a lot of us got our start. For some more advanced documentation, the deck The Riddle Of The Temple has a behind-the-scenes section at the end that explains some more advanced techniques.

I'll try to address some of the issues you're having.

The first thing that I find really helpful, that isn't really obvious, is that you can click the Decker option in the menu and then select "Toolbars". This will toggle toolbars on the left and right, which gives you drawing tools similar to MS Paint. It's the same as what you find in the "Tool" menu but easier to access. This can be helpful for drawing or manipulating images.

In general, a lot of the time if you're writing code to do something it's easiest to put it inside a button. If you create a button using the "Widget" option, then if you double-click it while in Widget mode (or select Widget->Properties from the menu) you'll get an option to change the text and shape, and also options labelled "Action" and "Script". For simple things like moving to another card or playing a sound, the Action option will let you do this without writing any code. You can just pick which card to move to, which transition to use etc. But if you need to do something more complicated then the "Script" option is generally where you put lil code. Anything in the "on click... end" block will happen when the button is clicked.

This should be hopefully enough to create like a zine, since you can have different cards and move between them with buttons, but if you want games like you described then you'll want to use the "dialogizer" and "puppeteer" modules. They're in the "Examples" folder where you installed Decker. If you open them up they'll have detailed documentation on how to use them, and to add them or any other modules or fonts to your own deck, all you have to do is drag the file into Decker, and it will pop up a tool to let you do that.

One good source of examples can be that a lot of games in the various Decker jams have unlocked versions, so you can open them up in Decker and look at the code and find out what it is they're doing and how they're achieving things.

Please let me know if any of this doesn't make sense, and I'll try to explain more simply!