How much can I improve my bacne scars? Will I be able to eventually wear backless clothes confidently? (photos)

From the photos provided, it is very difficult to say how much is active acne, how much is postinflammatory erythema and postinflammatory hyperpigmentation and how much, if any, scarring has occurrred. The most important point to emphasize is that the sooner that any active acne is brought under control and preventive treatment is initiated and the earlier actual scar treatments are initiated before the scars "mature," the better the ultimate cosmetic result. You would be wise to see a board certified cosmetic dermatologist asap who can help you with an appropriate regimen of in-office and at-home treatments to suppress any active acne and also to treat any incipient scars or even mature scars once the acne is sufficiently controlled. If this is done with alacrity and appropriatelty, the short answer to your question is that "Yes!" you will likely be able to go with backless clothes. Hope this helps and best of luck.