Broadcasting and buffering

Hi I have some big issue.. My Download and Upload is around 100mbit. But when others watching my stream or by myself its still buffering with 3500bitrate, even with 2500! I dont get it, already tried all the servers, all the apps and its still not working well :( Only good way for me was to set bitrate to 1200 but a quality is terrible and unwatchable.. I would like to hear some advices. Thx