I went to an investment company to work as a futures trader. They asked me to use virtual funds first and then pay me a salary. Is it credible?

It’s unreliable. Many similar companies recruit so-called traders and operators, basically under the guise of recruitment, trying to deceive “employees” into “customers”, and then turn “customers” into "The money was deceived into their pockets.

The principle is that as long as the company requires, mobilizes, or entices employees to pay for themselves or find relatives and friends to open accounts, they should leave immediately. Don't take chances or naively think that you are a genius.