Asking myself the same question, it seems hard while starting out especially for B2B.

A “good way” seems to be to cold call / cold e-mail businesses that would benefit from the product. This is sadly considered illegal in germany. The only way to get in contact with them would be if they sign up for a mailinglist, which needs a lot of marketing money. Maybe someone knows other good ways?

Attending events, conferences, etc. is not possible either during the pandemic.

2020 doesn’t seem to be a good year trying to start a company :(