how to do reply the script to a private message?

on *:TEXT:Hello:?:msg $nick Hi

Says "Hi" when people message you with "Hello".

this reply if text receive is "Hello" but if I would reply only if text contains word "mirc"?

Then change the word for the word mirc or use an if.

ON *:TEXT:*:?:{
if ($istok($1-,mirc,32)) { msg $nick message }
}

I like to use $istok you can use iswm or isin.

what means 32?

32 is the ascii number for the space character.

and to reply to a message sent on public channel?

/help on TEXT

ok, now I understand but you could say what are arguments in syntax... thank the same

but to have nick who chat in public channel? $nick doesn't work...

nobody knows how to have nick that chat in public channel?

In an on *:TEXT:*:#:{ event $nick is set to the persob who spoke.

Please read the help file, most answers you've been looking for are really all there.