If you have installed properly multi lang in your Jommla, select other language on the top left select list in the BreezingCommerce as shown in the picture below.
The go to the Orders > Status Manager > and there you can change every status as desired.
Let me know whether this changed the status language as you wanted.
To find the Orders > Status Manager go to "Commandes", but don't enter a specific order so if you are in one, close it.
Above you will see "Status Manager" button as shown in this picture.