To treat your skin concern
Use a Glycolic acid
or salicylic acid
face wash ( saslic or melawash)
Get your blackheads removed regularly
Do not squeeze or pick your lesions as it can lead to scarring and pigmentation both
Apply clindamycin gel and retino a cream over pimples
Apply kojic acid cream( Kojic) over pigmentation marks.
Apart from these an appointment with your dermatologist
is required for below mentioned treatment options
If acne is too severe taking a course of oral antibiotics
and isotretinoin might help
As you still having acne in your 40s, hormonal pills might be required too
Taking sessions of chemical peels
would help not only in scarring, pigmentation but also in treating active acne lesions.
Hope that answers your query.