There are multiple options to use concurrent languages.
The most common solution is to use long and short descriptions on the products and labor for each language, then, before running the report, apply the foreign currency feature, as explained here. This method, combined with a translated Proposal report, is simple to implement and satisfies most user cases.
This would provide a product (or labor) with two descriptions, one for each language, and depending on the language that you want to show on the report, you select to use "Long Description" or "Short Description" under the Report Settings. If the rate is different (and will always be), you apply the foreign currency and the day's exchange rate. The combination of this feature provides you with products with their correct description (in the correct language), currency value, and symbol.
Another option is to create a custom report and utilize a custom field for the translated description. This option allows you to use three different custom fields (long text custom fields) for the translated text to set support for four languages (original language plus three).
You may also download the CustomDescriptionProposal.dtr report mapped to use the custom field 13 instead of the description field.
If you need more information, please open a Support Ticket.