LexOffice Download File via Lambda

I'm trying to download a file in PDF from LexOffice API via Lambda Function (NodeJS, and Amplify) and return the result to the user who called the Lambda.

I am using NextJS with Typescript.

So this is the Lambda snippet:

            const resInvoice = await axios.get(`https://api.lexoffice.io/v1/files/${invoiceFileId}`, {"headers": {'Authorization': `Bearer ${lexOfficeApiKey}`,'Accept': 'application/pdf',                },            });            console.log(resInvoice)            return {                statusCode: 200,                headers: {"Access-Control-Allow-Headers": "*","Access-Control-Allow-Origin": "*","Access-Control-Allow-Methods": "OPTIONS,POST,GET","Content-Type": "application/pdf",                },                body: resInvoice.data.toString('base64'),                isBase64Encoded: true            };

And here how I handle calling the Lambda and download the PDF.

            const restOperation = post({                apiName: 'TeachpieRestApi',                path: '/getinvoicepdf',                options: {                    body: {                        queryParameters: {"invoiceId": invoiceId,"invoideFileId": invoideFileId,                        },                    }                },            });            const { body } = await restOperation.response;            const blobPDF = await body.blob()            // set the blog type to final pdf            const file = new Blob([blobPDF], { type: 'application/pdf' });            // process to auto download it            const fileURL = URL.createObjectURL(blobPDF);            let link = document.createElement('a');            link.href = fileURL;            link.download = "Test" +".pdf";            link.click();