Generally speaking, you don't need advanced mathematical knowledge to do business. What you need is sales promotion skills, a good grasp of the market, the preferences of people who may buy your things, the advantages of peers, and of course your efforts.

And you said that bad math will affect your business. I'm afraid you mean that bad math will make you a bad accountant. I don't know if you are losing money or making money. Then I'll tell you, it has nothing to do with mathematics, but with accounting knowledge, and you can hire an accountant after starting a business.

You said that your calculation is not good, you can choose to use a calculator or related software to help you calculate, and you are not required to check the calculation results for customers. Get 100 points to buy your things.

In short, the quality of mathematics has nothing to do with the quality of business. If so, let alone a mathematician. College students majoring in mathematics have long made a fortune by mathematics.