How to hide the toolbar buttons

I am developing in C # and would like to realize the following.

-I don't want to display the upper toolbar and left and right toolbars.
-I was able to hide the upper toolbar and the left and right toolbars, but when I hover the mouse cursor over the image when the toolbar is hidden, a black simple toolbar is displayed.
I don't want this to be displayed either.
-As a realization plan, the upper toolbar is displayed, but I thought it would be good if all the buttons in the toolbar were deleted.
I used ToolButtonRemove to specify the button I want to remove,
The button doesn't disappear even though -1 is returned.

I am using Acrobat Standard DC and Acrobat DC SDK.