If you need to display prices (the Money type of custom field ), then it is necessary to adjust the base currency on a DNN portal. The base currency is the main currency whose values you will add to the Money type custom fields. In case you use more languages on your site, it is possible to add other currencies to the currency list and adjust the exchange rate.
Your site is a real estate website. The main language on site is American English and the second is German. The base currency is set to USD, and an additional currency is EUR. In the Exchange rate field enter EUR to USD exchange rate. Finally, at Available languages you select German language and you add EUR as a currency that will be displayed on a German version of a website.
When you add an article (in this case an article is a real estate) you enter a price of a real estate in USD. Users who visit the German version of the website will see the prices in EUR, and the amount will be calculated based on the exchange rate you have entered for EUR. Exchange rate can be afterwards changed depending on currency change.
Currencies are adjusted in Dashboard > Custom fields > Currency Setup