What is the analogue of the agreement between LLC and SP by bank transfer will be the agreement between LLC and upwork and how to get it from upwork?

Question

Law in IT

Situation:
Amendment: LLC is a client (customer)
LLC worked with different entrepreneurs by bank transfer, receiving a contract, an act of completion of work, etc. LLC wants to work for upwork
Questions and problems:
1. LLC needs a certificate of completion for each contract from upwork. In other words, an LLC cannot transfer money from a current account without a certificate of completion and an agreement
2. Are there legal analogues of a document for each replenishment of an account with an agreement from upwork
3. As I understand it, an LLC must conclude a contract with Upwork for payment under the contract, and the performers work with upwork and will not have a legal relationship with the LLC
4. How will the agreement get legal force in Russia, since Upwork cannot, as I understand it, sign a contract either physically or electronically

Answer 1

(my numbering)
1. LLC must start foreign economic activity (FEA).
2. LLC must open a foreign currency account in a Russian bank next to a regular account.
3. Issue a transaction passport, etc., which will be required by the bank under a contract with Upwork.
4. Banks working on foreign economic activity will accept documents from Upwork for their acts, etc. according to foreign standards, incl. physically unsigned.
5. Transfer from LLC to individual entrepreneurs of contractors - it is necessary to conclude contracts with them and draw up acts in accordance with Russian law. And according to your point 3, the performers will have a contractual relationship with the LLC. They can be employees, but it's more expensive.
6. Apply for the simplified tax system 6% and the tax will not delve into the acts of Upwork.
7. Why do you need the legal force of an agreement with Upwork in Russia? I described relations with the bank and the Federal Tax Service, but you cannot sue them in Russia.