Remove sidebar black background rectangle

I’m sorry but as you are using a commercial theme, you need to seek support from the theme’s vendors.
https://themeforest.net/user/eugeneo/

In your stylesheet, both #sidebar and #footer have background-color: #0F1012; You’ll need to remove that line from both of those IDs.

Or, if you’re using a plugin like Custom Style, add:

#sidebar, #footer {
background-color: none;
}

solved… thank you very much.