Quote from: adska on May 18, 2018, 08:42:44 AM

Hello, I would like to create crypto exchange system where you can buy and sell bitcoins by PayPal.

This is contrary to PayPal laws

Quote from: adska on May 18, 2018, 08:42:44 AM

All payments would be executed by PayPal API. But I am afraid of possible Paypal API blocking of my domain.

yes, they will do.
PP ban any direct exchange into bitcoin (Because the scammers are buying bitcoin [irreversible] and then claiming they have not received anything )
The best solution for you is to create a site like Virwox [Users are allowed to buy bitcoin indirectly"not direct exchange"], Deposit money from PP, Buy a broker's currency, and then exchange that currency into bitcoin.