This I have from the Internet. Maybe it helps you to save a lot of time. According to scientific knowledge the following method can be used to permanently store a vocabulary in the long-term memory and never forget it again.

A new word is asked every day again until you know it right away.

If you know a word immediatly it will be queried again the next day.

Then after another two days;

then after another four days;

and for the last time in nine days.