HELP - paw issues?

[bones2013]

Hi, bones paws have what look like scars on them,
We went on holidays for a week and left him with friends.
Before we left his paws were missing some fur... I've never had a dog before so I thought because he was a puppy it would grow in... He is 15 weeks now.
So now it's worse, and our friends think he got burnt or hurt when he was a puppy. It's worse now, I think he might have mange? This is my uneducated guess ... Advice would be great thanks you

He is super smart and sits stays for about 15 sec and shakes a paw
No signs of abuse breeder said she had him in an outdoor heated kennel for the beginning of his life