Project Review

[GitMazzone]

Just to make you aware: you've uploaded much more than just your Colmar Academy project here, all in the same repository. Also, you've included several "final" versions of your index file rather than just including the most recent - I graded index3.html.

Don't use rem for anything but font-size - that's what it's made for, as it's a scale based on the default height of fonts. In your project, it causes lots of sizing issues that prevent your content from spanning the width of the page. It's better to use px or percentages for things that aren't text.

Here's a cheat sheet for flexbox, hopefully it'll be helpful: http://jsbin.com/yaroqun/edit?html,output
A goal of this project was to use flexbox styling to align your content within and around itself, so I'd recommend considering how you might go about simplifying your code with flexbox.
One example: your rightkp section and the divs within could have been accurately positioned with the use of justify-content: space-between, and the use of the column flex-direction.

The same basic fixes apply to all of your sections, so I think the best course of action would be to look through that cheat sheet and to rework your code, either from scratch or just adjusting what you've currently got to make use of existing flexbox positioning.