Add file API -> How should the request body look like?

Hello Everybody, 

I want to upload a file to HighQ with Power Automate.

I had no problem to solve this with Postman, but I have no clue how the body XML of the request should look like.

Currently I get the response, that my xml is not valid.

<file>here is the file content</file>

<filename>hieristhefilename.png</filename>

What <attributes> do I need to put on start and end of the body?

I studied all documentation (old and new stuff), but the information about the request body of all the endpoints are very poor. 

Every help is much appreciated. Thank you,

Philipp