My friend gave me an engagement ring with a diamond, the price of which is about BGN 1,400. I wore it, but later we noticed that the stone was cloudy and did not shine. We suspected that it was fake and we took it to several places and of course unfortunately it turned out to be just that. People were not unanimous whether it was a diamond or not, but they said either that it was not or that if it was of very poor quality and therefore not shown to the tester. In any case, the quality is not written on the certificate. In addition, from the inside, where it was installed, when they looked at it, they said that it was cracked and that the installation was not good. We want the jeweler to return the money, I keep the certificate, it was not bought for a long time, but he refuses. What can I do in this case Can we complain and where?