Enable this option in WPML
Go to WPML -> Settings -> Custom Fields Translation and set to translate these 3 custom fields: property_custom_details, extra_pay_options and extra_options
For Extra Custom fields
Add extra custom field in a property in front end
Translate the property
Access the translation in front end
Check String Translation and translate the custom fields
Check translation
For Booking Extra Options
Edit Property -> Price -> Add Extra Options
Translate the property
Edit the property in 2nd language in Front end and edit the labels in 2nd language
The property will show the labels in 2nd language