The colours are a bit intense, especially on the path page, especially the green. I think the red-orange nav works, but in some cases white or a very very light grey would be better.
You should read about flat design (or material design). There’s certain aspects of flat design which could improve your design, and it’s good to have some knowledge of flat design if you’re a full stack developer.
I noticed the caching doesn’t have an expiry set. This is relatively minor, but it made me think - if you’ve never used .htaccess files and you’re interested in learning the basics, setting when the caching expires could be a good chance to see what it does. There’s some code under ‘Browser caching for .htaccess’ which you can basically copy into the .htaccess file for the site (assuming you can access it): https://varvy.com/pagespeed/leverage-browser-caching.html
However you may want to read this first: https://varvy.com/pagespeed/htaccess.html