What do I do so that my macaws feathers could grow faster only his chest is bald?

Are you sure he doesn't pull his feathers out or rub his chest against things when you're not looking? Birds pull out feathers to line nests and it's sometimes a stress response. If he's under stress, you can try toys and activities but your best bet might be to get him a bird buddy. It often helps unhappy birds since they're very social and love having a friend to preen and play with.

If it's not a stress response, just make sure he has a good diet. Give him some cuttlebones or calcium blocks and give him fruits or veggies that he likes (if any–sometimes they're picky.) You'll just have to wait for his feathers to grow back, I think. But make sure it's not a behavioral issue.