To override CSS of parent theme

Neither padding: none; nor padding: -1; are valid CSS, and are therefore ignored. Removing padding: 0; from the parent theme is inadvisable as it’s “resetting” the (largely varied) default browser-applied style of many elements, and will likely create issues with other CSS on your site that expect such a reset.

You should specifically target the items you wish to change. So to add some space to the left of nested <li> elements, use new rules to add space to those elements rather than trying to remove the styles applied by the parent style-sheet.

ul>li li {
    padding-left: 30px;
}

Altering parent theme stylesheets is generally a bad idea if you are not the parent theme’s author.

You may want to check out this introduction to CSS to get a better grasp on CSS selectors and inheritance.