I need help, to hide the section of a button in html, this only happens when I visualize the page in mobile view, since, in desktop view if I can hide the selection box, here is an image to guide : 
I need help, to hide the section of a button in html, this only happens when I visualize the page in mobile view, since, in desktop view if I can hide the selection box, here is an image to guide :
To do this, you must apply the : active style to the button.
button:active{ background-color: transparent;}
If it does not work for you (I do not see your code to be able to assess it) you have another option:
Add ontouchstart="" to your body tag:
<body ontouchstart="">
Here you can find more information: link