Google API Oauth2 "insert subtitles" don't working

I was able to configure the oauth2 credentials for Google API in order to use it with Youtube.
I was able to configure an http request to list the new videos and I was able to configure an http request to download the subtitle for that video. Both of them work correctly.

However, the problem is when I want to make an http request to “insert subtitle” or, in other words, to upload a translated subtitle file. I keep on receiving that the body is not correct. However, I don’t know how to do it.