Thank you Michael Arts, In fact, I was reading this article and there is a lot of questions not answered in there, that is why I was wondering if somebody had the experience to do that in this forum.
For example wherein Mendix modeller, I can set up the URL and credentials for my external bitbucket?
In the picture, you can see that the only option that appears is "Enable Private Version control" and nothing else.
The preferred way is to follow these steps (link), where you can create an app with private Subversion based version control enabled AND platform portal features also enabled (like buzz, user stories,...)
The 'Enable private version control' enables the ability to upload a local project to a private Subversion based version control repo. You can configure the repository url via the menu Project -> More versioning -> upload to version control server... Be aware this will result in an app with private version control enabled, BUT with all other platform portal features disabled.