I have a Dane, now 18 months old...has no food or resource issues. All our previous dogs had no food aggression issues...here's what I did! Establish regular feeding time...after you eat. If it's not your food time...get the bowl ready with food, eat something, anything, then present the bowl to him. Give him 15 minutes...food gets taken away (refridge if necessary)...he waits til the next feed. As pups, my dogs never ate any food for the first month unless my hand
was in the bowl with the food in it. It takes time, but it is well
worth it. You may try this method or the one following, whichever you feel comfy with.....it will slow
him down as he will only be able to eat a handful at a time..your hand
with the food should be resting in his bowl.I feed my Dane 2x day, am and pm.
Another method....While he is eating, present a small piece of special food, (I use chicken chunks, you can buy it canned) slowly to him while he is eating. He should smell the food, pause, then lift his head from the dish to eat it, and then will continue eating his food. Little by little do this, getting closer and closer to his food while he is eating (no formula here, just get close enough before he starts to growl), give him the treat with "good dog" and back away. You should be able to eventually walk up, put your hand in his food while he is eating and he will take the treat. It may take time since he is older.
I have done this with all my dogs, and you can walk up to their food dishes while eating and anyone can stick their hand in it without them even pausing, as they are never sure if there will be an extra treat...they view it as GETTING something, not having something TAKEN AWAY. I would also suggest that if you mix anything with his food (I use plain natural yogurt, vet recommended for Danes), and mix it with your hand to get the smell of your hand on his food.
The one thing you shouldn't do is an 'ALPHA ROLL'...tho recommended by some, dogs resent it, and you rarely see even dogs do this.
Good luck
When playing with any toys, at the end of the playtime you wind up with the toy and put it away. Each time, you get and give the toy, and take it away after...this establishes you as the OWNER of all his resources. Remember Danes reach maturity at three years. One of the best pieces of advise I was given by a Dane breeder is never let the pup do anything you wouldn't want a 170# dog to do...especially jumping up on you...not even allow his tiny little feet to come on on you....they won't be tiny for long. Monty was never able to lift his front paws off the ground to rest on anything. Thanks heavens, as he is now 18 months old and 39" at the shoulder...an unusually big boy...can you imagine him out of control? To this day Monty will NOT jump up to anything...not even the SUV, we had to get a mini-van he could walk into.