You can use may instead of can. Sorry, may you please repeat it slowly? or Sorry, could you (please) slowly repeat what you said?

Can you say that more slowly please? or Sorry, can you repeat that more slowly?

Thanks, Su.Ki. , very clear.

Cinzia, please note - It is NOT possible to use 'may' instead of 'can' in a question like this. 'May' is for when you ask if YOU can have permission to do something. 'May I ...?' the translation of the Italian 'Posso...?' 'Potrei..?' ie for use with the first person (I) , not the second person (you). 'May you..' is wrong. Please don't use it!