Maybe uploading your files again will help. Sometimes, files get corrupted and uploading them again, fixes the problem. How do you upload your files? FTP?
I am fairly new at this latest release, but from memory, here are some tips...
Presentation is now Design.
The nav bar has gone from its usual place. To add or delete pages on your nav bar, you need to do that in the widgets section.
Static front page is done after you have written it, then go to Settings>Reading and set your front page there. It will give you a choice of which page you want to set as your home page.
Wordpress at the moment doesn't look good to me, either. However, we humans are creatures of comfort and don't like too much change. Stick with it, it is just getting used to the different way of doing things, that's all.
To add links to the nav bar @design/widgets from the dropdown menu select haeder then open up nav widget and add your links.
To change the fonts site wide it's @ design/layout towards the bottom of the page. To change them on a per post/page basis you need to declare a font class when writing your post/page.
@Peter As a non techie I know exactly where you are coming from - and I felt just the same on first encounter with 5.5. I wondered why Denis had gone and made such a mess of a great tool that I was just getting used to.
In fact I've just been building a new site and although the logic is a bit different in terms of where functions are located in fact it is even better than before with far more detailed control.
Just take the time to explore and read everything and get used to the new layout.