For your first test picture, did you have it on 'auto'? It's a stunning picture, but I've never been patient enough to learn about aperture and shutter settings. If I get a picture of that quality, it's purely by chance!
Pretend the camera is a tap for a water hose. The aperture is the knob that turns on the water. The more you open the tap, more water flows through. Shutter speed is how long you leave the tap open.
Aperture priority allows you to pick how far you "turn the knob". Wide open lets in tons of light but no depth of field. If you want high depth of field you let less light in through the lens by closing the aperture.
Shutter priority allows you to decide how sharp the photo will be. 1/8000 will stop a hummingbirds wings, or you may want to keep them blurry and pick a lower shutter speed.
So lets say for a perfect picture, auto mode takes a picture at 1/1000 of a second at f11. If I decide 1/1000 is too fast, (maybe you want some sort of blur) lets say to 1/500 of a second. Twice as much light is getting through at the same aperture, so a good picture at 1/1000 f5 is perfect, but at 1/500 will be overexposed. So changing the shutter speed one stop means you have to adjust the aperture 1 stop as well. In this case you want 1/500 at the next higher number f stop which is f16. 1/250 @f22 etc.....
f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128,
Every time you close the aperture 1 step you are letting in half the light. If we use lumens, @F11 lets say 600 lumens through the aperture, but at f22 its only 300, at f32 is only 150, etc...
Same for shutter speed. Every step up or down is 1/2 the light or twice the light if you go opposite.
But the cool thing is if you are in shutter priority mode, you don't have to pick the highest shutter speed. If I am in shutter priority and I want lots of depth of field, I want a high f stop number. So turn the shutter speed as low as 1/60th of a second for a hand held picture and you will get a nice high f stop number.
Depth of field is how far and how close things will be in focus. If I take a picture with a 50mm lens at f2, anything 2 feet in front and 2 feet behind the object will be in focus. if I set it up to f22, everything within 22ft of the object will be in focus. If you want to see your depth of field there is a button you can push that will show you what the camera actually sees. Normally when you look through your camera you see everything clear, but if you push the button for depth of field you are looking through the camera with the aperture closed at whatever point you have it set at. So at f22 it will be a very dark looking picture, but you will see how much is in focus compared to say f2
Ever notice pro photographers, taking blind pictures? Ie holding the camera above their heads and pointing in the general vicinity of the object they want a picture of, say some dude in the middle of a crowd? They are using an 18mm wide angle lens set at f22. Guaranteed, the picture will be in focus at f22. Everything within about 20-25 feet will be in focus in that picuture.