LangShop uses Fixer to setup exchange rate for selected currencies.
When you add currencies to your store, they are added with the rate, current at the time of adding. LangShop doesn't provide currency automatic update.
With "Grab new rates" button you can update the exchange rate to the actual state if needed:
- Go to "Settings" => "Currencies" section menu.
- In the right sidebar you can find "Exchange Rates" block.
- Press "Grab new rates" to update your currencies to the actual state.