There are generally three ways to stop unwanted website from Gmail. You go to your Gmail account and after pressing the subscribe button at the bottom of the message coming in the website, it will take you to your website and you unsubscribe.
In the same way, there are subscribe buttons for each website in every way. And some do not have a subscribe button, there is a photo and on clicking that photo you will go to that website and you will unscribe.
If such a subscribe button is not found, then you can unscribe by going to the three dot above and clicking on the block.