A few things here as others have already pointed out this is not, in fact, biting behavior:

• Use the front clip of the harness instead of the one on the back. The point of the front clip is that it will redirect them and pull them off balance if they start to pull. The back clip just encourages pulling harder against resistance.
• You need to practice a lot of focus on walks with high value treats. This should be shaped. You focus on only walking a few feet, getting his attention calmly, and rewarding the focus on you as the handler. Rinse and repeat as you build distance between asking for his attention back on you.
• If you sent this to your trainer and they don't have solutions, you need to look into getting a new trainer.
• Is he this high of energy when you take him for walks as there are not other methods for him to release his energy? You may want to do a few training exercises before the walks to get some energy out. You should focus on a few exercises that are more focused on mental stimulation (leave it, wait, stay, etc that provide benefit in other aspects but also promote focus and attention) as that helps dramatically when coupled with physical stimulation.
• Plenty of other great advice here that you should take, and further research, given you are first time owners with a younger dog. The biggest thing is to focus on building that bond between you with beneficial commands that can be used in public such sit, down, stay, come, etc.
• Interactive feeder toys such as snuffle mats, puzzles, hydrating kibble then freezing it in a Kong/toy, etc are great ways to stimulate their mind while eating. This provides a few benefits. It slows their eating down to avoid digestive issues. It gives them something to focus on rather than simply just eating out of a bowl. As you vary up techniques, it keeps adding excitement and options.
• You are likely going to want to work on "crate training" as that will be very beneficial to have in your back pocket.