Update: I’ve done it. I have decided to finish the last books I had for those languages and stop. It’s the only way I can put all my energy in my new future goals.
Thank you everybody for participating in this thread.
I have finished the book I had for German, and the book I had for French. Now I only have left the one for Spanish that it should be done in few days.
I add for posterity my beloved ranking results. 
But success comes only if we are able to take the right decisions, whatever the cost.
German: 1394 days streak
French: 380 days streak
Good luck for the others in the ranking.