Learning two languages at the same time can be amazing but also confusing. At college I study English, German and Spanish while in my spare time I study Japanese and Mandarin. People often ask me if I get confused between these languages. While the answer is yes, I still can differentiate between all of them and I will give some pointers on how to learn different languages at the same time.
While you're studying at college you often study different languages at the same time. Why aren't we getting confused in college then? It is because they separate the classes. You spend one hour completely focused on one language, do something else and then they give you one hour again to focus on something different again. You can apply this method out of the classroom too. You can listen to Chinese music while driving to work, make your grocery lists in German and read a book in French.
The key to this is to keep everything separated and make a routine out of it. But, if you are listening to Chinese music while driving to work you must only listen to Chinese music. That way your brain is able to get used to different languages and you have less chance to mix words up.
In my daily life I speak Dutch with my classmates, English at work, German with my father, Japanese with friends and Spanish in the classroom.
As for the amount of languages, I think you should stick with a maximum of two languages at the time. Also choose two languages that are not similar to each other so they don't overlap in the process of studying.
Remember that time is a luxury and haste is the worst enemy of quality.
I hope this will help you.