For the problem of Dandruff, before you wash your hair, put some coconut oil on your scalp and leave it for 15 - 30 minutes...then wash
Try to comb the hair after applying the oil on the scalp so that the hair strands get the oil also
if your scalp /hair is not oily and the weather is not humid/hot it’s better not to wash your hair too often...twice a week is enough
For the problem of Acne, my daughter had similar situation before and we went to see Private dermatologist。She took Antibiotic for a few days and recovered. She has been using a brand of Acne Gel which is quite Good. It can be bought from MannXXXX and is very cheap. The price is very reasonable......or you might try to ask for it from public hospital (HA). She also using a brand of Lotion for cold weather. So far so GOOD. For the brand name, you can PM me. For my opinion, it is too young for a 11yrs old kid to Go for facial appointments for the removal of acne. I think there’s a danger of getting cross contamination/infection in going to have facial appointments. It’s dangerous because the infection has the possibility of going to the brain.