You have way too much going on in there and you have asked several questions all at once.
Try breaking it down into separate questions and making reduced case demos for each with only the code necessary to reproduce the issue.
There’s no need to recreate the whole page in codepen..just the bits you’re having trouble with.
You’ll probably get the same advice on SO (I thought I saw this question there too).
Oh…and for your demos, you can add bootstrap and normalise via the options under CSS in codepen.