Language changed to english at checkout

I have only one language on my website. I need the language that I use on my site, “danish” to appear in Klarna Checkout IFRAME. But now everything is shown in English.

On Klarnas site I found this How it’s done

{
“purchase_country”: “GB”,
“purchase_currency”: “GBP”,
“locale”: “en-GB”,
“order_amount”: 50000,
“order_tax_amount”: 4545,
“order_lines”: [
{
“type”: “physical”,
“reference”: “19-402-USA”,
“name”: “Red T-Shirt”,
“quantity”: 5,
“quantity_unit”: “pcs”,
“unit_price”: 10000,
“tax_rate”: 1000,
“total_amount”: 50000,
“total_discount_amount”: 0,
“total_tax_amount”: 4545
}
],
“merchant_urls”: {

“terms”: “https://www.example.com/terms.html”,
“checkout”: “https://www.example.com/checkout.html?order_id={checkout.order.id}”,
“confirmation”: “https://www.example.com/confirmation.html?order_id={checkout.order.id}”,
“push”: “https://www.example.com/api/push?order_id={checkout.order.id}”
}
}

But could someone help me understand where to change this?

regards Christina

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