Hi @Dzianis_Malets,
Welcome! Thanks for raising your issue. I see your IP is part of AS24940, which I've received word from the team before that it is already allowed.
Can you check that you meet the Hertzner prerequisites for Elasticsearch as covered here in their support documentation? If you have been granted hos-dev by their support already please send me the tracing details as per this post.
Hope that helps!