recording second track

I cant hear original track when I record second track, mute button is not activated, not sure what is going on.

Edit menu > Preferences > Audio I/O
or
Edit menu > Preferences > Recording

Select “play other tracks while recording new one”.

The exact location and wording vary depending on which version of Audacity you have.
In future, post in the forum page that is appropriate for your version of Audacity and your operating system, and state exactly which version you are using and it will be possible to give a more precise answer. Too much information is better than not enough.