Unfortunately I’m not trained in training… but what I can tell you is that immediate, positive reinforcement is far more effective than negative. Their doggy brains struggle to connect the events so they understand we’re angry, but not why.

Prob teaching granny to suck eggs but I would get him a large collection of chewable toys (which he’ll likely wreck disturbingly quickly), when you catch him chewing something he shouldn’t tell him sternly “NO, BAD DOG”, give him one of his chews, then when he starts chewing that praise enthusiastically / give a treat. He’ll quickly associate chewing his own toys with expected, praised behaviour and chewing non-toys with bad behaviour. Try to be as consistent as possible; I taught my mum’s dog lots of tricks / behaviours through constant repetition. Conversely, all the good work I did with my sister’s dog was undone immediately by her knobhead ex; consistency and behavioural modification ‘in the moment’ rather than after is key (imo)