Overlay itself to improve bright sky dark ground

(You need Android Photo Editor (Macgyver) to follow the steps, see my earlier blogs on how to use)

Original dark photo (removed nadir and purple fringes)

Added same photo on top, screen mode.

Repeat to get a brighter image

Repeat again to get brightest image

Step 2, Edit> Overlay, choose different brightness photos for different zones

Use the mid bright photo as the base, overlays the entire upper part with the darkest photo, the in-photo-border must be soft whereas the image border should be hard or stitch line will show - simply extend the soft borders beyond tge image borders.

Then, overlay using brush tool, to adjust or enhance different spots: 

Lastly, use Edit> Colour, brush tool, to raise the darkest area, indicated in yellow above.

This is the end product.