I edited my site to be responsive some years back. Most things will shrink well enough, though s few of the pages can't because it would destroy the artistic vision/mechanics of the pages. I mostly just "care" that it looks good on anything from a desktop to a reasonably sized tablet.
Changing your div/frame sizes to percentages and using the viewport metatag that Bill suggested should be all you really need to do to make it responsive. It wouldn't be hard to do and besides, it's good edumication. :)
Actually the viewport is doing what is supposed to do... what you could do make sure that your elements aren't fixed width.
You could use percentages like this -> https://stackoverflow.com/questions/24299990/can-percentage-be-provided-in-iframe-tag-of-html5-tag-for-height-and-width You could also give them a minimum size, too, if you don't want your frames to shrink beyond a certain point. e.g. - width:60&; min-width:120px;