Language, Currency

Go to Theme settings > Language, Currency 
Why do you need config currency? This is a tool that helps you use multiple units of money in your store. 
For example: your customers are Australian, of course they will convert the unit back into Australia.
There are 2 different types for configuration currency:
+ Follow by Multiple Currencies by Shopify
+ Follow by Multiple Currencies by The4
1 - General 
1.1 - Enable Customer Geolocation
Boost up your sales by showing your prices in the Visitor's Currency! When a customer goes to your store, your store chooses the currency to use based on the geolocation of their IP address. The prices in your storefront and checkout convert immediately to that currency. If a customer's location uses a currency that isn't supported by your store, then the store's currency is used. For example, your store currency is USD and you accept USD, EUR, and YEN. When a customer from Brazil visits your store, they see prices in USD (your store's currency) because you don't accept payments in BRL.
1.2 - Show country Flag?
1.3 - Currency position fixed Center
A new option from Gecko5 allow you show currency in better position
1.4 - Checkout currency notification
This notification will appear on the cart page, shopping cart widget. It is meant to inform your customers that Shopify only allows them to Checkout in your shop's main currency.
2 - Follow by Shopify
Advantages:  
When you check out the product, you will be able to use the initial currency of your choice. 
Disadvantages:
 When you select other currency the page will be auto reloaded.
You can refer here for config:
Enabling your store to sell in multiple currencies
Shopify Help Center
2.1 - Step 01
Shopify admin > Settings > Payments
2.2 - Step 02
 In the Multiple currencies section, enable the currencies that you want to support from the list of accepted currencies.
Config your currency by follow this official guide https://help.shopify.com/en/manual/payments/shopify-payments/multi-currency#supported-currencies​
2.4 - Step 04
 Click Save.
3 - Follow by The4
Advantages:
When you change the currency you don't have to reload page.
3.1 - Step 01
Go to Theme settings > Currency converter plus > Source: Multiple Currency By The4
3.2 - Step 02
Settings > General > Change formatting
From the Currency formatting, replace the HTML from
1
${{amount}} or €{{amount}} or something like this but in different currency  
Copied!
to
1
<span class=money> (your above value) </span>
Copied!
Please see this screenshot for more detail 
3.3 - Step 03
Click Save and see the result (VND is our currency's country)
 
4 - Language selector
To add a language, go to your language settings.​
​Learn more about selling in multiple languages​
To work on translations, install a translations app that's compatible with selling in multiple languages. Visit the Shopify App Store​
4.1 - Show language selector
4.2 - Language position fixed center
Result:
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From The4
Hope you success!!