How to change my menu settings?

Hi there,

I’m new with the usage of WordPress. I’m using the theme Constructor and this is my URL: https://www.lindsayvanherk.nl. At this moment, I’m playing around with the menu tabs (creating them in “pages” – is this the right way to do it?). However, I can’t find answers to the following questions:

1) How do I remove “categories” tab from the menu?
2) How do I link “home” to the homepage?
3) I’m planning on creating a photography portfolio. Under the tab “portfolio” I’d like to create thumbnails (or something else if that’s not possible) with different categories like “nature”, “animals”, “portrait”, etc. How do I do this?

Any info on this will do, thanks in advance!