Need a Software or method for access Overloaded Website

Hi Our Business is process visa & immigration consulting for Bangladesh Nepali & Indian. we provide work permit and living permit in European countries for our clients. Since Long day we are unable to get the embassy appointment in poland & czech republic. cause embassy open slot for appointment twice in a week. Friday & Tuesday at sharp time GMT +1, 11:30. when it's time to book an appointment we found a message Server is Overloaded try later. we have tried in many way like using a Highest speed internet like 1 GBPS / vpn / some extensions. but nothing work. within 15-20 min appointment date are taken by someone and website become normal and there is no available date left. someone getting appointment every time. So i am looking for a software or method witch can help me to access this overloaded website and get appointments. this website ASP.Net based ..here is the website link https://secure.e-konsulat.gov.pl. and i have attached some pictures when the server become overloaded