The adjuster assigned to your claim works for the insurer. That is not an accusation, it is the job description, and it is the reason most business owners are the only unrepresented party in their own claim. You are negotiating a number with somebody who does this every day while you do it once.

Getting help does not have to mean paying for it, and the order matters. There is free help that most people never use, and paid help that is worth it in specific situations and not in others. Knowing which situation you are in is this step.

Have your inventory finished and your first offer in writing. Without a documented number of your own you have nothing to compare the offer against, and no basis on which anyone can help you.

Ask the adjuster, in writing, for the calculation behind the offer and the specific policy provisions it relies on. That one email does more than people expect. It is also free, it creates a record, and it sometimes produces a revised figure without anything else happening.