Is it possible to somehow add adaptability to a non-responsive template?

Question

css

Based on the finished layout, I made a backend for the site, and at the very end I realized that there was no adaptability. If I run the site on a device with a high resolution, or in the browser I set the zoom to less than 100%, it turns out hell on the site =(
In the front-end, I'm not very good at fumbling, more precisely in the adaptive, all my adaptive was always Bootstrap.
Is it possible to somehow add adaptability site without understanding the styles themselves already written, or is it unrealistic?

Answer 1

Well, if you used Bootstrap and its grid, it should work fine. Add to page header
All tables should be replaced with div elements.
Remove absolute values ​​and positioning.

Answer 2

If you want to "quickly and not take a steam bath", then set the width of the container globally through the viewport. For example,

<meta name="viewport" content="width=1200, user-scalable=yes">

then. the user will see a reduced scale of the site and will be able to zoom with their fingers on the device.
However, ideally you need an adaptive. On the neighboring stock exchange, you can throw off the TK and the guys will help for a symbolic reward.