Retently doesn't have a multi-language selector. Instead, you can fully customize your NPS survey texts and translate them in any language you need.
First, start a new NPS campaign. You will access automatically the Templates tab.
Feel free to create a new survey template or simply edit an old one. To customize any text in the template all you have to do is click on it. Then, you will be given the possibility to edit the NPS question, score labels, Open-ended question and Thank you page texts.