Based on your answers, good teachers are able to make a reliable estimate of the number of words you must transfer into your brain. This number varies between 5,000 and 15,000. Worst-case scenarios are languages that are completely different from any of the languages you know: for Europeans, typical examples are Hindi, Arabic, or Chinese. In these languages, only a handful of words resemble European words and leave you with 15,000 words on the table.