Good afternoon
From all the information you have provided, I would strongly recommend you to use a broad spectrum sunscreen (considering you are using a topical tretinoin/supretret) SPF 30+ UVA & UVB
Please make sure that you a using a sunscreen, 15- 20 minutes before you step out in the sun, reapply every 4-5 hours depending on the sun exposure.
Apply on all the sun exposed regions(face, neck, hands etc)
Once you wake up in the morning, wash you face with Salicylic acid based product(saslic face wash) apply sunscreen 15-20 mins before stepping out in the sunlight, reapply based on the exposure, once back home wash your face thoroughly with Saslic and you may apply the night cream/Supratret.
Discontinue Supratret once you have achieved the desired result.
Regarding the existing tan you can go for certain chemical peel which can be done at a cosmetologist/
dermatologist center.
Use a lower pH soap white non-scented soap and a good moisturizing lotion for your body when at home or before going to bed.
Stay well hydrated, eat healthy and sleep well.
Thank you