1.Please add following code into the custom.css:
.mobile-nav .menu li a{color:white}
Here is a video tutorial how to create custom.css: https://www.youtube.com/watch?v=Qok2zRedRMY&feature=youtu.be.
2. You may set sidebar in apearance-widgets->shop sidebar.Please clarify your request about sidebar with more details.
With best regards
Brian Johnson