Good start, but here are a few improvements that I can see in your code thus far:
Instead of using the ‘container’ class, use the ‘container-fluid’ class with BootStrap. See Documentation Here. This will resolve the issues that you are having with the grey background jutting out in some places.
Secondly, you do not need the Head declaration within your CodePen project, they should be defined in Settings > Stuff for < head > and you did not close this tag < /head > in your code either.
Otherwise things are looking like they are taking a good start. Let us know if we can assist with any further revisions!