But in general, I found some guy in Russia that agreed to sell BTC with a 20% fee.
Your money, your risk, and your responsibility - but 20% is simply too much, and there is also a guy from Russia who is unknown to you. This is an ideal combination to be scammed again, so when you are already going into such risky transactions, I recommend that you find a respectable escrow - ideally it would be one of the members of this forum who have been dealing with it for a long time.
Recommended bitcointalk escrow servicesGenerally this is better option to do since if he deny to have an escrow for that deal then provably that is scam in the making. But for better security I will just find way to buy bitcoin with less fee and I think binance offer that so better go at them and check if he's card is allowed to buy some bitcoins or other alts there.
We need to be aware that anything offer us anything huge which is shady well better back it off and find reliable things or option which we can rely on.