HTML CSS Flex basic JavaScript no Mobile section yet

Overall, your site looks good. But there are some things that I didn't liked.

1. The horizontal scroll. I think there is no use in it so, better restrict it.
2. Its not responsive
3. The positioning varies on cross-browser tests.

Some tips:

1. Don't give a fixed height to the header or footer because it destroys the responsiveness.
2. Don't use large pixel values instead use rem or em because they are much more responsive.

By the way good work, I liked it.

Hi, I have just read this article from Josh Comeau about transitions. I think it resolves the problem you had with the drop-down link. Check the section about Delays, he uses

.dropdown {
  opacity: 0;
  transition: opacity 400ms;
  transition-delay: 300ms;
}
.dropdown-wrapper:hover .dropdown {
  opacity: 1;
  transition: opacity 100ms;
  transition-delay: 0ms;
}

I think you can adapt the example to your page. I hope it helps.