How to adapt css for IE5-9?

Question

css

Yesterday I just found out that it turns out that my site is not displayed correctly by browsers IE9 and below. I bought a template for the site, turned to the seller (wp-city.ru), who "sent" it away, since I changed the color of the template, which disrupted the display of the site in the IE browser below ten. Or you need to pay him, then he will fix it.
I read a lot of literature on adaptation, cross-browser compatibility, etc. I tried something, but no result. What would you advise me, where to start, what to read, or maybe there is an expert on this kind of issues here?
Thanks in advance.

Answer 1

I advise you not to worry about IE9 and below, their share is almost zero

Answer 2

With the help of conditional comments, we hide what is displayed incorrectly and replace it with a similar one, but readable by older browsers.