I don't know how you're metering, but the second shot is exposing for the sky, so the foreground is underexposed. You're probably using 'evaluative' metering. I would recommend picking another mode. With evaluative metering, the camera makes the decisions. For learning purposes, it might be best to try the 'spot' mode. With spot mode, you pick something in the scene that is important, and you tell the camera how you want it exposed. It's an interesting exercise. If you're interested in finding a very simple book to explain how a meter works, try 'The Confused Photographer's guide to Photographic Exposure and the Simplified Zone System' by Bahman Farzad. It breaks down exactly what is going on in very simplified terms. It makes things very simple for you. I'm not trying to be condescending. I bought it early in my photographic journey and I found it very useful. We all have to start somewhere. No one is born knowing this stuff.
The second bit of advice that I can give you is to pick out a subject and fill the frame with it. What popped into my mind when I saw these photos is 'what is this a photo of?' Good photos have a definite subject. Even landscapes. Pick a definite subject. Look for 'leading lines,' like roads, fences and rivers. I can't say that I'm really good at the art of landscape shooting, or anything else, for that matter. My photos are mediocre at best. But I do know that good photos often follow certain rules. I recommend looking at the photos that you feel are good, and study what's going on in the photo. How did the photographer compose the photo? How does the light illuminate the photo?
I'm really not a great photographer myself, but that is not the point. Photography is not easy. If it were just about buying expensive gear for perfect results, it wouldn't hold any interest for me at all. Taking a good photo is a learned art. I recommend looking around this site for examples of great photography. This community has a large number of really great photographers. Best of all, they're real people who are here to help. Most of the time they'll tell you how and why they shot what they did, if you ask them.
I hope that my ramble was helpful, and I hope you don't take it as a harsh critique. Like I said before, we all have to start somewhere. If you want to take better photos, you'll have to work at it. I know I have had to do that. I'm still not a good photographer, but I think I'm improving. I photograph because I love it, not because I'm naturally good at it. I'm sure most people on this site would say the same thing.