I urgently need to access a site that for reasons unknown to me is blocked by my ISP. Maybe someone can tell me what tools or methods there are to bypass the blocking quickly and easily?

You can bypass your internet provider's blocking very easily by using unblocked browsers. These are browsers that help bypass absolutely any restrictions and give their users unlimited access to absolutely any resources on the Internet, including those that are blocked in their region. You can learn more about how to choose one of these browsers here https://gologin.com/blog/best-unblocked-browsers.