Opening Port 53 in Centos 7 Configre DNS With Bind

[Yadro]

I Configure DNS with Bind, open port 53 on both tcp and udp all configuration is ok NS propagated properly (check on whatsmydns) but when access to my domain its retrun with "THE CONNECTION TIME OUT the server mydomain.com is responding slow or too busy" how to resolve this issue little bit confuse right now where i made mistake any help will be appreciated.