this solved the error connecting to database error
wp config create --dbname=mywordpress --dbuser=myuser --dbpass=myrootsqlpass

this solved the Unable to determine linked PHP error
create /usr/local/sbin folder and reset permissions
sudo chown -R 'whoami':admin /usr/local/sbin

check error logs to resolve 502 Bad Gateway Error
/usr/local/var/log/php-fpm.log