How to fully close a section or separate them because my text has a clickable link

In line 78 you have a tag <a href="...">.

It should be followed by a closing </a>, but I don't see it. Without that, the linking will occur for all text and all elements that follow it.

Either the closing </a> is hidden from us due to horizontal scrolling, or (quite likely in this case) you forget to add it, or you removed it, or it got displaced to a strange location further down.

Besides that... your HTML is very messy...

I advise that you make it more tidy by indenting it nicely. There are great tools for that. Doing so would also help you to spot such errors more easily by yourself.