Yes, cases are not like German, where you had aus bei mit nach seit von zu and those were all the preopositions that governed the dative. Russian has a lot more. But, as I and the Canadian have suggested, just go at it one at a time. Learn one thoroughly then go on to the next. You probably won't be speaking fluently for a couple of years. I have been at it for nearly a lifetime and still screw up all the time.