Congratulations!

You only seem to have 9 ratings in the App Store globally (7 in the French Store, 2 in US) so far for 57523 downloads as you say. I used the iTunes Search API to obtain this info for your app id (I'm contemplating a move from iOS programmer-for-hire to full-time indie and this Python script is part of my market research).

That suggests only about 1 in 6391 users bother to give you a rating on the App Store, which is very low from what I hear: the usual figure quoted is 1 in 100 to 1 in 1500 for free apps. If this is right, it might be worthwhile to ask users in-app to give you a rating on the App Store if they like the app.