I need a mentor![Pls Read]

So I want to make YouTube videos.

But my friend said that my voice is not good, So I asked some people they say that.

• Most of the time I talk from the neck not the tummy.

•They also said that most of my voice goes throught my nose.[They suggested to talk by Closing/pinching my nose, like "mmmm" and said the vibration should be in Mouth. But when I try I can't produce "hmmmm" with close nose and feel the vibration in nose.

I CAN'T YOU, BUT I WOULD APPRECIATE YOU TIME AND HELP.