So, I mounted my $5 garage sale Kalimar 800-1200mm f/9.9 to f/14.9, roughly the equivalent quality of the lens the OP used in this thread, on my Sony a7r3 full frame 42.4 megapixels and shot a tree, in Raw, that is about 50 ft. off my deck to see what it would be with minimal post processing. Camera was tripod mounted on a sturdy Bogen 3063, IS on, and shot was triggered by hand. The first is the middle of a 3 shot bracket at 1200mm f/14.9 and the second is an hdr processed in Affinity with that 3 shot bracket. I processed the Raw files with Photolemur then gave them some minor levels, contrast, saturation, brightness, and shadow then downsized them from 350dpi to 72dpi, no sharpening. B&H sells this lens for $149.95 and there are several on ebay ranging from $100 to $189. https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=Kalimar+800-1200&_sacat=0 The lens is okay to "tinker" with but it is anything but a pleasure to shoot with. If you are meticulous, in your technique, which I'm not, it will probably produce a pretty good shot. The tree trunk on the left was less than 5 feet from the one in center so for 1200mm it is wide open at f/14.9 and it shows in the depth of field sharpness. I would expect to see similar performance out of the one the OP used. No sharpening was applied beyond what Photolemur may have done in the Raw conversion so I'm sure that could be improved on. When you take it up to 100% as it was shot at 350dpi it has green freckles everywhere. Looks like I need to set my time a little better on the a7r3 - wasn't shot at midnight.

Absolutely true!!!

I have many m42 manual lenses (and also more modern manual only Samyang/Rokinon lenses) and can get perfect focus with my mirrorless cameras. I consider them my fun lenses and just love using them. I have autofocus lenses too. But the manual focus ones are just a joy to use. I just love the precision manual focus rings that are so smooth to turn. When I try manual focus on my AF lenses, its not a good experience at all. Some of them have really short rotational travel from nearest to infinity and it is just not easy to get a good manual focus.

And I really, really hate manual focus on focus-by-wire lenses.

Something else I really don't appreciate are the cameras that as soon as you turn the focus ring, the camera automatically magnifies the image. I want to focus magnify when I want to focus magnify and not when the camera wants to do it. If I haven't framed the image yet, I certainly can't while magnified.

My 2-cents!

It is difficult to photograph active subjects with a manual focus lens. There are some techniques that help, but overall your best bet would be to invest in a good autofocus capable lens.

That said, one thing that can help is to stop the lens down for more depth of field. That way some minor focus error will not be a problem. To do this you're going to need to use higher ISO (and possibly a slower shutter speed). There's a limit, though. A too high ISO will introduce a lot of digital "noise" in images. It will also reduce image contrast by compressing the sensor's dynamic range. You'll have to experiment with your particular camera to find your limits.

Another thing that can help with moving subjects is to pre-focus when you can. Observe your subject to see if there is a place they repeatedly come to and set up your focus on that spot, then wait for them to arrive and take your shot when they do. This isn't always possible... but a bird at a feeder, for example, will often use the same perch each time they approach. Some sports follow a predictable path, as do moving vehicles. It all depends upon your subject. Some other sports like volleyball or basketball are highly unpredictable. Or, a baseball pitcher is pretty predictable, while an outfielder is a lot less so.

When you can, use the Live View on the rear screen of the camera to focus more precisely. Often cameras have option to "zoom in" on the Live View preview to really closely check focus accuracy. The larger screen on the rear of the camera is bigger and better for this than the viewfinder, too. It's not "zoomable" either, in an optical viewfinder like a D3200 uses. (Some mirrorless cameras' electronic viewfinders allow zooming in, but the screen in the viewfinder is still quite small compared to the one on the back of the camera. ). Of course, this won't work well with active subjects.

Still in Live View, I don't know about the D3200 specifically, but some cameras have a "Focus Peaking" feature. This draws a bright color (usually the user can choose from several) around subjects that are in focus. This can't be done in your camera's viewfinder. It's only possible with an electronic preview, such as is being done in Live View (or an electronic viewfinder on many mirrorless cameras).

I am not very impressed with the quality of that lens... It appears to have a lot of chromatic aberration ("CA"... look at the green in the out of focus areas). This is not uncommon with telephoto lenses. High quality telephotos use fluorite and other special elements to reduce or eliminate CA. Those lenses are a lot more expensive, though. Another thing critical with lenses is color rendition or fidelity. It looks to me as if there's quite a bit of loss with that lens. Images are low in contrast and somewhat de-saturated.

Some things can be done in post-processing to help the image... though there's a limit.

First, as some previous responses have noted, your images are massively under-exposed. I suspect they might look "okay" on your computer screen, assuming it's uncalibrated. Most computer screens are set up for gaming and/or office work and right out of the box are way, way too bright for accurate photo adjustments. This causes people to make their images way, way too dark, either in-camera when taking them or later when they post-process them. There are calibration methods and devices that can help with this. One of the first steps is to reduce the brightness to a more realistic level. After that a calibration device runs a series of tests to create a color profile, which is applied to the screen all the time so that you don't mis-adjust your images. While it is possible to calibrate reasonably well "by eye", it's not easy and takes a lot of practice (and a lot of wasted ink and paper with a photo quality inkjet printer, to be done right). A calibration device is a much better solution for most people. One will cost upwards of $100... But since any computer monitor will require calibration every so often, because they lose brightness and change color rendition gradually over time as they age, a calibration device is an investment that can see many years of use and if you do much printing will pay for itself in savings of ink and paper by getting you pretty close to ideal with your first efforts.

I hope you don't mind, I downloaded your 2nd cardinal image to see what could be done with it. I first did a lot of exposure, contrast, saturation adjustment, then applied some sharpening to just the bird. I also added a little more blur to the background, because that can make the subject appear sharper by comparison.

See what you think (might appear "too bright" on an uncalibrated computer screen)...