You are most likely having post-inflammatory hyperpigmentation of the acne that has recovered.
You also have active acne breakouts, therefore, for a treatment that targets both issues, I would highly recommend chemical peels.
Salicyclic acid peels can calm down and stop acne, while Jessner’s peels can reduce hyperpigmentation.
Subsequently you will need topical creams (e.g. Arbutin) for further pigment reduction, and acne products (e.g. salicyclic acid wash, retinA creams) for maintenance.