How to reduce or adjust Time To First Byte (TTFB) in nginx?

Question

Nginx

The site is loading, based on the analysis of the first problem, a long server response:
11092 ms First Byte Time
ms Target First Byte Time
There is also this message "Waiting for free sockets to connect took too long. The reason may be browser restrictions or too many simultaneous connection attempts ."
Has anyone experienced this? and where to get better Configuring Time To First Byte (TTFB) in nginx