This is a mixture of ideas about style, punctuation and choice of words.
My suggested changes:
I want a word to say that someone does not understand me.
I say something and he behave
s without noticing what I
carefully said.
I want to know what such a behaviour
's name is.
(I
may have made mistakes while asking this question ,if so warn me .and make me aware of my mistakes please.)
If the person did indeed hear what you said, but chose not to respond, you could say:
"I say something, and he ignores me.)
Ignoring somebody is a type of human behaviour, so there would usually be no need
to say that someone behaved as if ignoring someone else.