I don’t know whether my visit helped or not, I hope that it did.
I have zero experience of Andy’s camera, I looked it up and it seems to me to be perfectly capable. The camera that I took along was my Nikon D7200, a fairly basic and quite old DSLR, which I think is easier to use, but they should be roughly comparable in terms of image quality.
His long zoom isn’t as long as it appears to be, what is said to be a max FL of 300mm is in fact 145mm, Photoshop says that it is “35mm equivalent to 290mm” and that’s a bit of a disappointment.

To illustrate this, here's a shot with my camera, 200mm lens so 35mm equivalent is 300mm
Also, the front elements of these lenses aren’t recessed, they’re pretty much flush, and a lens hood is absolutely essential, but not supplied, so I strongly suggested that he get a cheap rubber lens hood to get around this problem. He also needs a better tripod. In my view, that’s the only money that needs to be spent.
In terms of technique, all sensor sizes have their limitations, with these micro 2/3rd cameras the limitation is that the small sensor size stops the lens from being stopped down very far, optimum image quality, avoiding diffraction limitation, is probably achieved at f/5.6. That’s the largest aperture that a lot of variable f/stop zoom lenses can be used at, with decent image quality, and also the smallest that totally avoids the general loss of sharpness created by diffraction limitation. Having said that, Andy took shots at f/5.6 and f/22 for comparison, and the loss of quality at f/22 was less than I expected.
My general advice?
Forget, for now, about taking photos of butterflies, bugs and birds, too difficult and with too many variables of distance, speed, depth of field and so on. Concentrate on the basics and learn the physics, and do this by photographing subjects that don’t and can’t move, i.e. subjects found in the home. That’s how we learn – or at least that’s how I learn – because when a subject keeps absolutely still, it’s much easier to nail the other variables such as camera height, light angles, choice of aperture, exposure and so on.
I also made the point that there is nothing basically wrong with his photos, he just needs to change his approach, concentrating on the physics-based element to ensure correct choices of aperture, shutter speed etc., which will leave his mind free of technical considerations, allowing him to concentrate on the artistic elements. Most of us would benefit from that approach. And none of us should compare our results, almost straight out of camera with just very minor tweaks to curves etc., to many of the examples we see online, which often owe far more to extensive post-processing than to the actual photography.