First byte and start render

Hi to all,
I can’t fix this problem with ttfb with my website, I optimized all as possible but ttfb is so slow and start render too, I spent many money and seems any developper have a solution for me :frowning:
website is
Anyone can help me to find possible issue blocking rendering?
So many many thanks!!

What servers your website is on? What is the tcp congestion control algorithm you are using? What is the tcp initial congestion window set too??