How to conduct IP correctly?

Question

Individual entrepreneur

Plot:
There are customers from Russia and international
There is payment in rubles and foreign currency
There are companies and individuals
And all possible intersections between these derivatives.
Who solved this problem?
Or at least how and to whom to ask this question?

Answer 1

Foreign currency and ruble accounts are opened in banks, foreigners pay for foreign currency, ruble for ruble. There is some trick that the currency is converted into rubles every day at the rate of the Central Bank, this needs to be clarified, I don’t remember.
It is more difficult with individuals - they can only pay if they have a cash register, in addition to special types of activities such as UTII or the patent system.