Sorry for the late answer. Sometimes I enter into the dark ages through a time machine, and later I come back.

Oh yes, it is a very easy grammar, created in a way that helps memorization: every substantive ends with o, every adjective with a, every adverb with e and so on, without exceptions.

Well, the issue of the number of speakers is one of the unsolved difficulties in the community. Most Esperanto-speakers are not part of any Esperanto organization, so the calculations differ widely. But the official number (of well-known speakers) is around 2 million esperantists.

Thanks for being so kind. !tip