The new image is slightly better than the earlier one (10,000 colors vs. 5,000) but still a low base to work from.
You might improve it a little bit. Something like this: https://i.imgur.com/AvEYHX2.png
Using standard Gimp tools
Duplicated layers, working on top layer (addition mode)
Remove the blockiness - use Filters -> Blur -> Selective Gaussian Blur twice: radius 3/delta 8 then radius 0.4/delta 34
Top layer in addition mode, add a layer mask, Layer -> Mask -> Add Layer Mask paint out any parts that are too bright.
New from visible, any small corrections
Final sharpen Filters -> Enhance -> Unsharp Mask default values.
A video of the process: duration 5 minutes
direct link https://youtu.be/4kmcn6JO0iI
You might improve it a little bit. Something like this: https://i.imgur.com/AvEYHX2.png
Using standard Gimp tools
Duplicated layers, working on top layer (addition mode)
Remove the blockiness - use Filters -> Blur -> Selective Gaussian Blur twice: radius 3/delta 8 then radius 0.4/delta 34
Top layer in addition mode, add a layer mask, Layer -> Mask -> Add Layer Mask paint out any parts that are too bright.
New from visible, any small corrections
Final sharpen Filters -> Enhance -> Unsharp Mask default values.
A video of the process: duration 5 minutes
direct link https://youtu.be/4kmcn6JO0iI