Hello Dear. You may continue the use of kojivit gel which is based on
kojic acid.
However I would rather recommend you to replace kojivit gel with Vitamin-C based creams.
The soap you have mentioned is fine, but make sure you are following a good facial routine which means cleansing, toning and moisturizing.
Also I hope the soap you are using does not make your skin over dry, as this could be one of the reasons for dullness.
I would better recommend a face wash which is more gentle and hygienic than a soap.
You may try
cetaphil face wash and moisturizer depending upon your skin type and you can also tone your skin with rose water sprays regularly.
As per a recent research, Vitamin-K based creams work much better for skin moisturising along with improving the blood supply, regenerating the broken capillaries which are responsible for dullness over a period of time.
Hope i have answered your question. Feel free to contact me if you have any more questions. I ll be glad to help you.
All the best
With warm regards
Dr Sanjay Kini