Is money earned considered permissible if a customer speaks with a girl in a normal conversation that does not violate religious principles in an internet cafe, and does this ruling change if the customer is a foreigner speaking with his girlfriend?

A man's online conversation with a non-mahram woman is permissible out of necessity and to the extent of that necessity, but most of it leads to evil. You must prevent the use of your premises and devices for impermissible conversations between the sexes, for what is forbidden is not limited to obscene language but includes every conversation that leads to what is unlawful, because means share the ruling of their ends. And a Muslim is not permitted to be a means for an unlawful act between any two sexes. As for the money earned, if the service was rented for an unlawful purpose from the outset, then the rent is forbidden. But if the rental was for something permissible, with the renter committing an unlawful act, then the rent is permissible.