Hi @gearmobile,
Welcome to the community 
You need three collections for this.
One collection for parent category like Sections.
Another one for root category like categories.
Another one for sub category like instruments.
And then you can have a list of sections and add a link action to the list to another screen to show categories and you can link that one to another screen to show the instruments or if you need to display all in a one list you would need a custom list and another two custom lists inside that list.
And for filtering how you want it to be?
Let us know how it goes!
Thank you