Why it says מכל and not simple כל?
Could be also: You ignore all what I say.?
Well, הִתְעַלֵּם is literally "to hide oneself from, to shut onself from, therefore you need the seperative מִן.
I don't quite understand. Shouldn't this sentence be for a male speaker?
yes it should
Why is 'You ignore all that I say' not correct?
Can i omit מה?
את מתעלמת מכל מה שאני אומרתתתתתת
At mit’alemet mikol ma she-ani omer.
"You disregard everything I say" should be accepted. Reported.
Should it not be מהכל instead of מכל since הכל is everything and כל is each?
There is no response to why is "מה" required.
Well, everything that is כׇּל מַה שֶּׁ־. You need to specify, what kind of every it is, as it could be כׇּל מִי שֶׁ־ everybody who or כׇּל דָּבָר שֶׁ־ anything that etc. too. Bare כֹּל with a suffix would be persons too: כֻּלָּם שֶׁ־ they all who.