Evening bites and aggression Great Dane puppy

by Maria P.
(Ostrava, Czech Republic)

Hi, we have a beautiful (nearly) 4 months old blue Great Dane, named Goliath. He is generally mellow and responds quite well to commands like sit, down, stay and leave-it.
Tipically he will be nice and well behaved all day and loves to nap and relax during the day. My husband and I have training sessions with him in our garden during the day (generally 10-15 mins each) and walk him twice or 3 times during the day, for a total of an hour per day or so. The biggest issue we have been having with him is his biting: he will do it at times during the day, generally stopping when we say "leave it" (when he gets a hold of our sweatshirts or pants). In the evening though, and especially after his last meal (at around 7-7.30pm ish) is a complete different ball game. He chases us and bites and grabs our pants and t-shirt and won't let go, growling at the same time. When we finally manage to get him off of us and grab his collar to make him sit, he will growl even more and open his mouth wide trying to reach backwards to get to our arm/hand. When we eventually force him into a sit or a down to calm down, he will struggle even more and the vicious circle goes on and on until we give him a time out to his crate (outside or inside) and walk away. He will then whine for a few minutes and then settles down. There is no telling what happens when we go back to him. Usually he is calmer, but very often he goes back to doing the same thing in a matter of minutes. We have him already signed up to a puppy obedience class, which will start this week. He seems to love people and other dogs and has never shown signs of aggression, but does get bitey with small children. Sorry for the long description but wanted to give as many details as possible. My husband and I are very concerned about this as he is growing at a scary-fast pace and we definitely do not want to end up with a mouthy and aggressive Great Dane!! Is this something to worry about??Do they eventually pick up the concept that they shouldnt be doing it, should we continue doing what we do now? PLEASE HELP! Thank you very much in advance.