I really like the sunset, but there are a few things you can try to improve on it.
If you can't do a reshoot then I would try the gradient filter. But if you can do a reshoot, or for the next landscape like this you may try these things.
Shoot the photo at f8, (f15ish if you want more foreground in focus) shoot at as low of an ISO as you can.
Use a tripod and a 2+ second timer so at low shutter speeds it will still be sharp.
Your camera can most likely take bracketed photos (nearly all do these days) if your camera can, then bracket a stop to a stop and a half high and low (this depends on your camera, some can only bracket three, and others can do more. If you need more brackets than your camera can do, you can bracket manually) with the multiple exposures you can do exposer blending. There are lots of YouTube videos on how to do this, but you have to use PhotoShop.
For sharpening, I use a "High Pass filter" in photoshop. To do this you first blend your photos and do any cloning or other change you want to make, then "Merge" all of those layers together, then duplicate the photo by using "Ctrl 'J'". This is the layer you use the high pass filter on, set it for 2.5 to 3.5, too big and it will look graining, too small and it won't be noticeable, so play with it until you like it. You can always delete the layer and start it again, or use undo. You can then duplicate this sharpening layer to add more and use a layer mask to make it more specific in areas. You can adjust the "Opacity" on the sharpen layer if you think it is too strong.
I hope this makes sense to you, PhotoShop can be hard to explain.
