Salut bienvenue sur le forum (sorry you said you wre french so..)
Welcome here, and enjoy, to answer to your questions :
Top 50 doesn't exist anymore, now it is the arena, but the rank isn't based on score. If score really looks good for you, you must know that 10men broke the 1 000 000 score more than a month ago and chromatophore too. Essence is around 900k, willng and pervepic are somewhere between 800 and 900k I guess. Then I dunno people with 700k. I'm currently a 627k, then all the master, Jappert, vagman etc have also a good score 300/400/500k..
You can get shards when you win vs someone in the arena, in pvp1/2 or in the special spin ( when you chain wins in a row) in arena too.
You can't have nymphs in spins because they turn into relics when spinned. Oracle can give you nymph and winning touney or event can give you a reward code for nymph.
You can ask me anything you want here or PM.