I have been told that don't accept payments via paypal, is that right?
Because when buyer will have his bitcoins then he can claim back money from paypal by saying that i haven't received desired product.
Yes they can do that. That's the one advantage of Paypal. Also, fees are too expensive in paypal and the transaction is not easy to do since you have to fill up forms. Whilr in bitcoin, you just need the wallet address and there is no more extra stuff. This is quite easier and less expensive.