Small update, the feedback from customer care is too generic and not focused on solving the problem. They gave me only generic info, as an answer to specific questions.
I don't think I will buy anything from this brand in the future if this is the assistance is basically null,
Thanks for reply! I just tried another android phone of same brand, it seems working. For unknown reason with P30 (2019 model, not so old) the piano songs are not present, the keyboard yes,. With p40 model both are ok. Hard to find a reason, considering that the songs (I suppose midi files) are the same. A bit bad that Casio brand don't offer any help with sofware and pass the buck on the seller ,If I had known, I would probably have looked at other brands. Next step: I would like to find the app folder and check if it's possible to extract the songs, to paste in favourites folder. Fngers crossed