It seems to be a fungal infection in your left armpit. I suggest you see a dermatologist to look into the rash, and get a medication accordingly. Deodorant should also be avoided as it might make the situation worse.
 

Sweating is your body's natural way to cool down. Certain medications can increase sweat production as a side effect or be symptoms of underlying medical conditions. Anti-sweat tablets reduce sweat secretion but may interact with your current medications. It's crucial to consult your doctor for a safe solution. They can adjust your medications or suggest alternative treatments to address the root cause of your sweating. Always communicate openly with your doctor about any concerns or changes in your medication regimen to ensure your health is prioritized.

The best way to get clear skin is to use a gentle skincare routine that includes cleansing, toning, exfoliating, and moisturizing. To help reduce the appearance of acne scars, you may also want to consider using a product with ingredients like retinol, vitamin C, and hyaluronic acid to help reduce inflammation, promote collagen production, and improve hydration levels. Additionally, you may want to consider using a gentle exfoliating scrub or mask, such as a clay mask, to help remove dead skin cells, unclog pores, and brighten skin. Lastly, you may want to consider using a topical spot treatment with ingredients like salicylic acid to help reduce inflammation and break down any remaining acne scarring.

Without a proper evaluation and diagnosis, I can't say. But normally, suggested treatments for perical pigmentation include topical medications and laser treatments and I do not recommend flutivate cream for pigmentation. However, based on your individual condition, the doctor will recommend the best treatment for you.