Overdubbing questions : newbie

i’m new to Audacity. I wanr to record myself over a backtrack.
I dont have sound card yet, i make test with the internal mic.
So i opened the backtrack, i have two tracks showing, i open a new track, select it, and when i record, the cursor goes at the end of the backtrack and record my voice on the backtrack’s track at the end of the track.
So it’s not what i want…
How must i do? My preferences are “overdub enabled”…

Many thanks for help…

There are two Record keys. Regular “R” key and “Shift+R.” One starts a new track and the other adds your voice to the old track.

You can change what the keys do in Audacity > Preferences > Recording > [X] Record On A New Track.