Problem with Media Query

Hello I am trying to make a static website for my projects.
I successfully developed the navigation bar responsive but the problem is when I am shrinking it to mobile size after clicking on the hamburger, I only get four links. Please someone help my in this issue. The link to the codepen is : https://codepen.io/deepslatex/pen/KKmZROR
Thanks for reading.
Regards,
Deepslatex