It's too long for curls ? Maybe I should get my hair cut in layers or shoulder-lenght ? 

I do not suggest cutting it!  Try what Curlgirl64 suggested, or maybe pin curls.  I don't have hair as long as yours, but I have a lot of it so I take a smooth roller and wrap my hair around it and then slide the curl off and pin at the scalp with pin curl pins.  I prefer these to bobby pins cause the bobby pins can leave dents in the finished curl.

Good Luck-tell us how it turns out!