Iframe Header Problems

Hello, I’m new to this forum and don’t forget if something is wrong with my topic.

I’ve been using HestiaCP for a long time and it’s very simple and everything is great… but what makes my site jump… some guy registers a domain and uses my website as an iframe… I’ve been looking for a long time how to block it, I’m trying to add a header to nginx but I see that there is already something against iframe. I’m not an expert, so I’d like to ask someone to help me… I don’t want someone to make money from my pain and my effort… If someone isn’t