Good going on getting your portfolio done! And I really like that you took to the challenge of completing it without Bootstrap. The main thing really is that your website is not responsive, so the mobile view could really use some help. Bootstrap makes that easier, but you absolutely can do it on your own without Bootstrap too.
Here’s a tutorial I found that breaks it down really nicely how to create your own grid system to make yoru website responsive. Hope it helps! http://j4n.co/blog/Creating-your-own-css-grid-system