Problem with footer

General CSS queries can be asked in general CSS forums such as;
https://csscreator.com/forum
https://www.cssforum.com.pk/
https://css-tricks.com/forums/
https://www.welovecss.com/
https://www.codingforums.com/

Or you could try using a browser developer tool for this kind of exploratory CSS work.
I used Google Chrome’s built-in Developer Tool just because I find it particularly easy to expose underlying HTML and CSS as compared to Firebug.

Now that you know the style, from being exposed/added by the Developer Tool, you can add a new style to override it.

You ought to add new styles externally, not within the theme’s files. Changes to the theme’s files will compromise the theme and be compromised when the theme updates.

External changes can be made using a Child Theme or through a plugin that provides Custom CSS functionality.

I recommend using the Jetpack plugin and its Custom CSS functionality to hold your CSS modifications.

luckily, your theme seems to have its own custom css file.

if the above suggestions don’t work, please try and contact theme-junkie for support;

commercial themes are not supported by this forum – apart from general suggestions.