malware – Unknown code on my website

Sorry for my english …

The last weeks I come often on my site these "comments".

{"name": "BryantFlogy", "email": "cgorillamail@gmail.com", "message": "Hello,
htmlkurss.xyz I've visited your website a few times
and decided to give you a positive feedback because I find it very
Good game. I was wondering if, as a person with experience in
creating a useful website could help me with my new site by giving
comments on what I could improve? You can find my site by
search for & # 34; casino gorilla & # 34; in Google (that's the gorilla
online casino thematic comparison).  I would be grateful if you could
take a look at it and tell me what you think about it. \ "casinogorilla.com
Thanks for the help and I wish you a good week! "
"datetime": "04/28/2019 01:44:49 pm"}

Can someone explain what he likes, what is he doing?

Many thanks !