Hey @sunnyson, thank you for replying.
I am doing post requests with a json of the collection-type which I want to create. These json are transcripted by the xml code of an edmx framework file and are properly formatted for strapi.
Here I attach two screenshots.
This are the requests done by strapi when you create a collection-type.
And I tried to replicate those requests with this code.
I hope that this information makes it a little bit clearer.