CallBack API bot is dumb, how to optimize?

Question

API

In general, the fact is that I made a bot. He replies everything is fine.
But there are moments when he does not answer for 30 seconds, sometimes more.
As far as I understand, the bot has a limit of 20 requests per second, which is not a little.
1200 requests per minute. As a matter of fact it is 1200 messages.
So, the server on which the script is loaded by 1% By the
way, everything happens in waves. The type seems to be postponing responding to messages and then sharply again to blunt everyone reads.
The script has a bunch of conditions. Everything is in 1 file.
What do you think, what could be the problem?

Answer 1

I looked, in general, events in the group come with a delay.

Answer 2

This is VKontakte itself stupid.
I have a bot, I use it only for myself, 1-3 commands per day, the server is not loaded at all. And the bot sometimes does not answer for 5-10 minutes.
It turned out that VK does not always immediately send requests to the server according to events. The message came, but the callback api did not work