I've lived in Kolwezi for 18 months and frequently walked around town both by myself and with my husband...never had any problems. Like any place you have to be sensible, I don't walk alone at night but generally the people are friendly and you only have to say bonjour and they respond in kind. I've also used local taxis and shopped on my own all with no issues. There are the same social problems as any city, homelessness, petty theft etc but I lived in Sydney before and it's just the same and there are certainly places I wouldn't go on my own or at night there as well.
i would suggest getting some sort of pouch to carry your passport in rather than a pocket or handbag, it's required that expats have them with them at all times, I have a pouch that goes around my neck just in case I lose my bag or it gets stolen, I also carry minimal bank cards with me simply because if you lose them it's pretty impossible to get new ones. Again the same measures you would take when you travel anywhere.