You would need, in no particular order:
1. To sell via platforms such as eBay or Loupe Troop, create the link, then cross-post in PS. Please refer to the rules about listing pre-loved jewellery on PS.
2. Better photos, in different lightings, such as indoors against a white background, outdoors in the sun and on a dull day etc...
3. Tell potential buyer what is so special about the cut of this Topaz in your listing
4. Tell potential buyer know the provenance of this Topaz and how you could back it up that it is a "Precious" Topaz
5. Price guide on what you are looking for
I am not an expert on selling, hopefully, the experts will come and offer their advice soon.
I would be prepared to not make much money. 1. because the cut isn't very good (from what I've seen), and 2. You'd have to somehow prove that it's "precious" or "imperial" topaz
Welcome!! @dk168 did a wonderful job advising you of some selling tips. And one I would repeat is... quality photos of the stone in natural light. Good luck!