Hello,
I use Audacity: it's free, and you can decrease the tempo of a piece without changing the pitch of the notes.
If you play regularly, you will find a tempo for which you can hear the notes.
To transcribe them, I use Musescore, also free and great.
Of course, you need to know a minimum of music theory.
If not, you learn the notes at the speed that suits you and then you play it at the right speed.
Musically
Cavag31