Conclusion of a contract with a foreign customer. What subtleties, pitfalls can expect me?

A contract with a foreign customer is coming, under the contract I will receive a certain amount of money every month. Since for me such a new process - some questions have appeared:

How should the contract (contract) look like so that it could be possible, for example, to submit to the bank (as proof of the legality of the money I receive from abroad) or as proof of income (not sure if it will be)?

Interests, in particular, should there be a copy in Russian? The main points of the contract, which are important for me, which are the most urgent to pay attention to?

I would be grateful if there are people at Habré who are ready to explain such subtleties.
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Thank you in advance.