If I got it all, he asked sight unseen, if she 'had a lot of Belgian Malinois in her' because of the description of her as being a sharp hard dog. A knowledgeable dog person would not ask that.
A knowledgeable person might ask for her registration info, or if she is a purebred, registered German Shepherd, or if she was a cross. Would NOT ask if she 'had a lot of Malinois in her', because a knowledgeable person would ask if her sire or her dam was a Belgian Malinois and if she was a cross.
A knowledgeable person would not ask what he asked, partly because it indicates a bizarre idea about Belgian Malinois, as well as about GSD breeding and traits of working dogs in general.
Dog doesn't look anything like a Belgian Malinois, anyway. It looks like a German Shepherd.
Belgian Malinois is toward the bottom, but this is a very fun site as it shows the different types and contrasts them with Malinois and Dutch Shepherd:
http://www.shawlein.com/The_Standard/13_Breed_Type/Breed_Types.html
Not someone I'd meet anyplace, especially not my place of work. Possibly at the K-9 unit where he claims he works, but only after he gave me the name of his commanding officer and I made an appointment with him. But like another person said, police dogs aren't usually acquired by individuals from ads like yours.
My first concern would be if he is legit, which I doubt. My second concern would be what happens if the dog flunks the class, which I would expect an older dog with her problems to do.