Does the second wife inherit from the business that was started with the first wife's money? And is it permissible for the husband to bequeath this business to his first wife? And do his children from the previous marriage inherit from this business?

If the company was started with your money, then maintain full ownership in your name now, while estimating your husband's share for his work, either as a sum of money or shares. If your husband passes away, his wealth, including his share in the company, will be divided among all his heirs. If the official documents are in your husband's name, then he should correct them now, or write a will that documents your original right to the company. He should not bequeath anything from his personal wealth to you, for the Prophet (peace and blessings be upon him) said: "Indeed, Allah has given every rightful person his right, so there is no will for an heir."