[Plugin: Polylang] Translating WP website without plugin

Hello,

I have WP site based on WP theme. I used child-theme to edit A LOT of the css (I changed backgrounds, added some totaly new elements that weren’t included in the theme etc.).

Now, it’s time to translate the website to English (my default language is Macedonian). I tried the polylang plugin BUT when I translate a page, the background image (which is added via css) is changed to white and I only get the translated text.

Can anyone suggest what’s the problem? Are there some pointers on how to translate WP website without using plugins (Books, tutorials, lectures)?

Thanks in advance,
G.