Welcome!
There’s no reason to feel bad. Think of Anvil as an introduction to some super-powerful tools, all at your disposal. If it’s frustrating, I suspect it’s because there’s no clear path from where you left off (C64 Basic), to here. (Forest-for-the-trees syndrome.) I’m going to suggest a path, below.
Bear in mind, this is just my own personal take on my learning process. Each person is different, and builds connections their own way, from a different set of starting points. Ideas “click together”, for each of us, at their own pace.
Having programmed in many versions of Basic (including Commodore 64), I can see how Anvil’s world would be jarring. Many of the rules essential to programming in Basic are completely broken in Python. (No line numbers, for example.) That doesn’t mean that the language itself is broken, but that it “thinks” about many things in a very, very different way.
It’s a good way, though. 
Far fewer shackles, far fewer details to get mired in, and many good ways you can organize things, when needed. Things that never existed in C64 Basic. As you get used to the climate, I think you’ll love it here!
The environment in which the language operates is also, conceptually, very different. In a C64, Basic essentially IS the computer. In Anvil, Python is operating inside someone else’s Web browser, inside a computer that may be half a world away. Anvil does an absolutely fantastic job of simplifying the whole mess, but it can’t fully hide all that.
So, you are tackling not only a different language (Python), but also all the layers built on top of it, at the top of which is Anvil. Even with Anvil, hiding most of the details, that is still a very long list of differences to digest all at once.
It’s not that you have an “old brain”. I’m over 60. I felt the same way, jumping into Java and its tooling and eco-system, all at once, a couple of years back. I failed. And that’s with a literal lifetime of programming experience, to shore me up. Too much detail, all at once, can mess anybody up.
So, how do you eat a programming elephant? One bite at a time.
Fortunately, this subject is layered. And each layer stands on its own, so it can profitably be learned that way. Working one layer at a time lets me learn faster, because I’m much less distracted by all the parts that lie outside that layer.
So I would encourage you to start with the foundation of it all: the Python language itself, in isolation. No distractions.
For getting familiar with Anvil’s version of Python, on its own terms, may I suggest Skulpt? It’s the same Python, just working in your browser. It has its limits, but this would go nicely with many tutorials on Python v2.7.
Just a few no-pressure hours here can do a world of good. Tinker to your heart’s (and mind’s) content, just to see how things work, and how you can make things work. You can’t “break” anything, so try everything!
The next layer up is Python’s Standard Library: functions and classes that were created to work with Python. It make more things possible, or at least easier. A lot of it won’t make sense, until the foundations are clear, though, so tackle this when you decide you’re ready.
You don’t need to learn the whole Standard Library. It’s arranged in chunks, by topic. Just browse the chunks (modules) that seem interesting to you. Get the gist of what those parts offer to you.
The main point, often, is just that the Library is there, ready to support you. I’m a pro, and every day I still go back to the Library documentation, looking for easier ways to do things. There’s way too much in that Library for me to memorize. (Never mind the hundreds or thousands of additional libraries you can get, for various tasks.)
Anvil strongly leverages these standard layers. So, once you’re comfortable with those, Anvil’s ideas – and mechanics – will be substantially easier.
