Sorry,
it is clear that as a web agency you do not look at the problems that merchants have:
Some cases to change the order:
1) the customer misses the product
2) the customer is wrong
3) the customer wants to change the payment method
4) the customer reverses the billing address with the shipping address
5) some items are not available
etc etc
The change of the language, however, is used to be able to sell abroad and the customs documents must be in English, currently prestashop makes the invoice in the language of the prestashop employee, in 2020 it should be possible to change the language to automotic without having to enter the database.