Then I installed Recalbox 6.1 on a new micro SD (unfortunately I only have a 32 GB memory).
First I performed a complete formatting using the software:
https://www.sdcard.org/downloads/formatter/index.html
Then as recommended by some guide, I started guiformat.exe completely deleted any remaining partitions:
http://www.ridgecrop.demon.co.uk/index.htm?guiformat.htm
So I uploaded the image on the microSD, started the system, connected to the Wifi, copied the ROMS for Advancemame and this is the result. Still slowdowns and audio problems.