Every language student comes across this question sooner or later: Is it possible to learn more than one language at the same time ? I'm going to talk about my own experience.
In a certain moment of my life I had to juggle with 4 different languages at the same time. I was 21 years old, if I am not mistaken, and I had a lot of free time that year. I already spoke quite good English and I wanted to continue improving so I signed up for B2 English lessons in the school of languages and I took a look at the other languages that one could study in that school: French, Italian, and German. The problem now was, which one should I choose?
I could already speak a little French since I had studied it in primary and secondary school and I really enjoyed it, therefore it would be easy for me to do English and French at the same time. Italian is well-known for being an easy language for Spanish-speaking people so it was another good candidate. German was the most exotic and difficult language that you could learn in my city back then. So which one did I choose? All of them! Did I mix them? Go on reading.
The answer is yes but not all of them and it wasn´t so confusing as to regret it. I just got confused with the two roman languages (French and Italian). I remember that in the oral exam of French I wanted t say that I had two sisters (J'ai deux soeurs) and what I did is saying the word "sisters" in italian (sorelle) but in a French accent so I ended up saying "J'ai deux oreilles", quite funny. On the other hand, I didn't have much trouble with the grammar, I would even say that it helped me even to undertand my native language.
So, should you start adding a second or third target language? My answer is yes, definitely. As long as you have time and motivation there is no problem in studying as many languages as you want. Remember that every different language is stored in a different area of the brain so this will help you differentiate one from the others.
Have you already tried? Please let me know your own experiences!