Hello @stefania,
It would be much easier to investigate your issue, if I had access to your dashboard.
Could you deactivate all plugins except the ones needed by the theme, to see if it is not caused by some incompatibility with external plugin?
If it is not possible to share administrator credentials with me, could you tell me what PHP version are you running on your server and if there are any errors in the JavaScript console?
Thank you,
Piotrek