Are child processes sufficient?

Question

linux

Web server: physical server consisting of 6 cores, 128 GB of RAM and ssd drives.
Often complain about 502 when accessing the site.
A request with a connection to the database often falls into the log of slow scripts. And because of this, just 502 appears.
php-fpm configuration file:

pm.max_children = 150
pm.start_servers = 36
pm.min_spare_servers = 24
pm.max_spare_servers = 48
pm.process_idle_timeout = 5s;

At the moment php-fpm is running over a socket.
Maybe there will be some recommendations.