The Trouble With Learning Multiple Languages At The Same Time
If you learn more than one foreign language sometimes it's problematic to keep them apart. Especially when trying to find the correct word in one language the other language may pop up instead. When you have a strong passive vocabulary in a language this will subside. When you're learning from a regular course or through generic communication your vocabulary will remain sparse and weak. Around 500 words are all those used in communicating, and maybe a 1000 words are learned from most full courses. The turning point is when you start to read extensively.
Extensive Reading in Multiple Languages
When you are reading, you encounter hundreds of words per hour, depending on your fluency. One Bermuda Word e-book contains more words than any full course. And this reading and re-reading strengthens your passive vocabulary. Words are also remembered in context of a subset of words or a sentence, which will give your memory the support it needs to remember these words more easily in case you want to use them actively. When reading you are strengthening your memory. And Bermuda Word e-books make reading fast since you don't have to look up any words, and the e-books also make it easy to remember all those new words, as the spaced repetition supports memorizing.