If your only exposure to words is the spaced repititon why are you wasting your time learning? Use the language and soon you won't need the repitition at all. The app is good to start because you need a couple thousand words before you can do anything, but in a few months you should be switching from learning words to reading and listening (and soon after writting and talking). if you do it that way most words will occure far more often than the algorithm suggests and become easy