If languages are from same family you can mix up words, but if you are studying languages from different families you will not have problems. You need just more time and patience.

No problem to Learn more than one Language at Once , I don't think that any mixed up with the vocab. e.g. I Learned English , Deutsch , and french at one time and nothing happen , for many reasons Cez the difference in sounds from language to another , .. and I could separate. I my Opinion its diffecult to happen any mixing up especially the Languages which you learning have different Letters , Sounds , Forms ,.. e.g. If you Learn English and Chinese "Mandrin" or Arabic at same time no fear in that case cez everyone of them have a unique Character than the other , May be Happen the Mixing up in my Opinion if you try to study two or more than one with many participant point like Letters , sounds , many similari ties in the Shape of Vocab. e.g. among Spanish , Portuguese , Italian , and French kinda .

Of course, it's good, at least that's what i think. Learning many languages makes us be able to speak to the people from other country, and it's absolutely break the barrier.

it depends on what languages you want to learn.. for example if you learn french and spanish at the same time.. the words can get mixed up at first. But, if you learn japanese and italian at the same time i dont think so.