JPEG is a compressed image format that contains less information than the raw files. This is normal.
In Lightroom, click on Export as... then JPEG, size = original (or Largest Available), quality = 100%.
That will be the full resolution image. You can verify the pixel count by right clicking on the image and selecting Properties.
Yes. Professional lights are amazing.
For static subjects you can use manual focus to practice. Using a tighter aperture (f/4 to f/11) will get more in focus (deeper depth of field). As a general rule, you don't want to increase the aperture over f/11 as that will introduce diffraction, which softens the image.
That camera has a couple of autofocus modes and watching any good video guide will introduce you to them. But for architecture it's good practice to try manually focusing too.
Crank that ISO baby. 12800 is acceptable for me on a full frame body. You can always clean it up in post.
Obviously, limit your shutter speed if possible.
Everyone else answered your technical question, I'll just say that the f/1.2 lenses are usually found on 56mm or 75mm lenses, which give them the same look as an 85 f/1.8 and 112 f/1.8 respectively.
These are still very capable portrait lenses... and while you would notice a difference side-by-side with full frame lenses, it will be slight. Reviews and sample images:
Viltrox 75mm f/1.2: https://sonyalpha.blog/2023/10/18/viltrox-75mm-f1-2/ vs. Sigma 105 f/1.4 (FF): https://sonyalpha.blog/2018/10/16/sigma-105mm-f-1-4-dg-hsm-art/
Check out Simon D'entrement YouTube channel, he has a couple of vids about composition so you can see examples.
Some typical composition tips:
Make sure your photograph has an interesting subject. Common mistakes are having no subject, or too many subjects. The photo should have a clear subject so we know who the main actor is.
Avoid harsh midday sun. Colors are better in the early morning or late evening. Usually you get about 5-10 minutes of truly spectacular sky colors in the morning and the evening, and you need to be set up in the right place at the right time to get it.
If you must shoot in the midday sun, use shade to your advantage. This mellows out the harsh sunlight.
Choose interesting angles and perspectives. Everyone takes snapshots from eye level at 24 mm (1x on phones). Get high, get low, and use different focal lengths.
The bright center and darker corners you showed in the image is lens vignetting.
The circle may be worsened by a filter. Interference filters permit light to enter perpendicularly, so you can get artifacts around the edges. The issue may be a combination of the filter and vignette.
For now you can manually correct for this in Lightroom: raise the corners, lower the exposure overall, crush the shadows, and increase the contrast until the sky appears even. There is also specialty software for this correction as many lenses suffer from it.
Next time try stopping down the lens one or two stops and make sure lens corrections are turned off.
Here is your real answer:
Stick your eyebrow against the top of the viewfinder. HARD. This works with or without glasses. Honestly, I usually leave my glasses on because that gives me distant vision and the ability to scan for subjects.
So in general, stick your eyebrow against the viewfinder, and peer through the viewfinder through the top of your glasses. Takes a little practice, but you'll get used to it with time.
Why on earth would YOU steal the government's photo comrade?
I zip everything up, and use OneDrive with an expiring link and a password. Typically, the link is good for 90 days.