Cleanto front-end (booking form) labels font is manageable. You can use any font from the drop-down of "Google Fonts" according to your website design.
Step 1: Go to Cleanto Admin -> Setting - > Appearance -> Front-end fonts ( choose accordingly )
Step 2: Follow the path and set whole labels accordingly for Front-end Booking form. Admin->Settings->Labels->Choose Language->Front Labels ( Set it accordingly ). On the another hand please follow the path of this article they will help you for set your whole labels. See Language Translation