how to remove voice of someone talking in the background?

Audition is the right tool, but don't expect miracles. You may be able to get to a point where the background voices are less distracting, but it is impossible to remove them completely. The biggest problem is that they are likely within the same frequency range as your main subject, so altering the background voices will almost certainly alter the main voice.

Hi Jawed!

Thanks for writing in. You can try Adobe Audition. Here's a link that shows how to: https://helpx.adobe.com/in/audition/how-to/noise-hiss-reduction-audition-cc.html

Let us know how it goes.

Thanks,

Kartika