
Hi Guest
Have you taken him to training classes, so that he knows how to recall back to you? If not I would suggest this, it should be fun for both of you and teach him what a recall means.
Have you tried taking a pot of tidbits with you, give it a shake and call him, open it and give him a treat (make them tasty treats), don't fall into the trap of just calling him back to be put on the lead, try it at first when there are no distractions around.
If he is a puppy, it will be asking a bit much to keep him to heel at all times off lead, he will need some freedom. Watch you don't over exercise him off lead, a large dog like that should have very restricted exercise while his bones are growing.
A halti will help you control him while on the lead.
Why don't you register as there are a few Great Dane owners on here who could advise you further.
Sandra