Individuals buy a company's equity (unlisted company), which is about 20%, so I have the right to enter the company.

If an individual purchases the company's equity (unlisted company), according to the law, you have the right to participate in the company's dividends (in proportion to the shares, unless there is a special agreement). As for whether you can enter the company, such as vice president or director, it depends on the agreement when you buy it. There is no agreement, unless the two sides reach a consensus again.