How to Handle too many tabs (sections) in MS OneNote?

You can use "Section Group". They help to organize your sections. To create one, simply right-click on a section name or anywhere on that bar above the page, and select New Section Group.

There is not a built in method of archiving within OneNote.

There are, however, ways to make your own manual archive.

The simplest would be to create a new notebook and manually move items into it that you no longer need.

A better option may be to more aggressively organize your notebook so you have fewer sections (tabs across the top) and more pages. OneNote itself should be able to handle a large notebook just fine, and if you're looking for a way to decrease the number of tabs, this is probably how to do it best and most easily.

Though you cannot automatically archive, you might consider making your whole notebook an archive and starting a new notebook or even several. Drag over any notes you need right now.

I use around a dozen notebooks, each for a different subject. Some date back years to the early days of OneNote and are rarely used but always only a search away.

Search is the best thing (well actually one of many "best things" ;) in OneNote. Since you can even search hand written notes and audio/video files.