It's quite clear that i should exchange my usd cash to ars on "blue market".
The question is- where exactly do i go to get this rate?
Some particular recommended trusted exchanges? or you usually find an individual in some FB group?
No banks, no debit cards, no credit cards. Those all go through the central bank and will give you the official rate.
You should ask around to see where they will exchange in your neighborhood. I've found kiosks, chinese supermarkets, restaurants that have done it before. There are also "cuevas" that are dedicated to changing money. Obviously it's important to always know the rate before changing. I find that most places will exchange around the rate shown on ambito - https://www.ambito.com/contenidos/dolar-informal.html .