Hi and welcome.
I would suggest you go to a vet for a skin scraping if you suspect mange (this will tell if it is mange and what type, you can't tell by a photo). I too echo Haltonhill Boxers in recommending you feed a good quality food - alot of the ailments that affect dogs are diet related. Check out
Dog Food Analysis it rates the different dog foods by their ingredients, it is recommended you feed a food that is rated 4 stars or more. Also here is a link to some info on
Hair Loss in Dogs, it covers some of the causes of hair loss and also touches a bit on natural remedies and supplements.