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