Now I received a very useful e-mail from support which I would thanks for the simple indications as well I would thank the developer of the Extension.
I am not going to use the payed features for this web site because it is based on a volunteer basis (and I am volunteer for it) but I will do it for any professional website it would require its features.
For sure I will post this review and my rating at Joomla! Extensions Directory.
My very best wishes,