Is it possible to make my nose flatter and rounder? (Photo)

You need a very good surgeon expert in fine works and specific requirements; yes, your dorsum can be flattened, you do not have any dorsal bump, your profile is straight however too high and distant from the maxilla, needing shaving but... not the standard hump shaving, therefore you run a terrible risk of ending in a saddle nose deformity (over resected dorsum) if you end in unexperienced hands; there is a specific method and planning how to lower a dorsum without a hump removal, which are different technical gestures (shaving bump are not equal to lowering dorsums).Also your tip has to be deprojected according to the new dorsal level set, which indirectly will round your nostrils.Finally, regarding the triangle you mention at the columellar base it is cause by some fibrotic tissue and open medial cruras footplates, which can be plicated to the midline or even resected to smoothen the triangle.Yours is a 8 out of 10 difficulty case due your very subtle requirements, needing a very precise and skilled surgeon.If you wish better grounded opinion please do post or send privately well lit, focused and standard images: frontal, both lateral and both oblique views, also underneath the nostrils.
Feel free to request any additional information from me.

IN my opinion your nose looks beautiful.  My advice is not to touch it.  And that's my professional advice.

Your nose looks excellent. The small changes you desire are not worth taking the risk of surgery as sometimes you can end up with a worst nose. RegardsDr. J

Hello and thank you for your question.  It is difficult to tell for sure based on your
photograph, but based on your description and goals, you may benefit from a nasal tip deprojection.  Make sure you specifically look at before and after
pictures of real patients who have had this surgery performed by your surgeon
and not just a computer animation system. The most important
aspect is to find a surgeon you are comfortable with. I recommend that you seek
consultation with a qualified board-certified plastic surgeon who can evaluate
you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon