Can't Enable İcloud Photos

I bought 50 gb icloud space to upload my photos to icloud but i cant do it.When i try to open icloud photos it says "can't enable icloud photos you can try again or see moro options in "photos" in settings."Also it says "photos synced from itunes will be removed.sycing photos via itunes is not supported when icloud photos is turned on. 675 photos will be removed." I don't care about photos.I tried to delete photos on gallery but there is no delete options.What should i do?