Please be aware that langify's currency switcher doesn't have its own mechanism for changing currencies. Similar to a theme's native currency switcher, it is based entirely on your currency setup in the Shopify Payment settings.
This also means, that issues related to currency conversion need to be addressed with the Shopify support directly.
If you cannot use Shopify Payment because it is not available for your country, then please have a look at a third-party app for currencies, for example Geolizr. Such currency apps usually have their own currency switchers.
Note that if the currencies are managed via a third-party app, the currency will revert to your shop currency during the checkout process.
Where to find it in langify
Go to the langify dashboard and open the Switcher Configurator. Here you will find the option to add a currency switcher.