Feedback for Portfolio page

Please feel free to critique this. Tear this to shreds. The more specific and tangible the better!

Well, it’ll be nice to add fixed navigation, and in Portfolio section if you look closer, you’ll see that existing examples are falling from their containers. I suggest setting 100% height for .thumnail in links. Then it works fine.
Also, there’s a problem with “Contact” part on small screen.

And, man, you should really reconsider the choice of background pictures : ( If its just for a challenge, and you don’t plan using this work as your real portfolio page in future, then well, it may be as it is. In other cases, I suggest looking for best practices at awwwards.com and there’s a site with free psd, where you can find templates for portfolio: https://psdrepo.com/tag/free-psd-website-templates/