Do you know why the sun has changed shape, and doesnt look very much like a circle?
post processing?
Whats lightroom? Can you not use photoshop instead?
The sun looks squished due to atmospheric distortion and clouds, that's all.
Post processing is when you edit the photo in software - so, adjusting white balance, vibrancy, EV and the like

Photoshop does pretty much everything Lightroom does, but Lightroom is designed specifically for photography - whilst having all the usual editing options you'd use on a photo in photoshop, it also acts as a library for your photos.