[alex123pavlov]

I found a lot of plugins for this query. But somewhere there is no such function and somewhere too loaded with plugins.

Limit the number of weapons to the number of players per team.
0 ak-47 < 8 player (CT+T=7player)
1 ak-47 > 8 player (CT+T=8player)

If a player tries to buy a weapon he writes an error in the chat.

admin can always buy weapons.

Thank you for your time

[ThatOneGuy]

I'm not sure exactly what you mean, but I think this might be what you are looking for:
https://forums.alliedmods.net/showthread.php?p=950174

[alex123pavlov]

It is too large and conflicts with some plugins and bugs.

[alex123pavlov]

There is no simple such plugin?