my experience
Hello
Re-activating the topic I found interesting
I'd like to give my support to anyone who is learning 2+ foreign languages at the same time. From my personal experience, this is (very) possible.
I'm 15 (second year of high school) and my school puts emphasis on classical languages, i.e.all students study two classical (ancient greek and latin) and 1-3 modern foreign languages.
As foreign language(s) are taught also in elementary school, at least one from modern foreign languages is on "continuing" level, i.e. "advanced".
From those modern, I take english and italian on advanced level, and french on beginning level.
Also, I study russian outside school (course at colledge department).
So that would be 4 modern + 2 classical languages
(english is not my mother tongue, that's why I count it here).
Of course, I don't think I know yet some of these languages (classics and french), but within years that'll change I hope.
Trust me, it's perfectly possible to learn 2+ languages at the same time. Of course the best would be not to start them at EXACTLY same time, i.e.have at least few months of distance (at least half of a year ideal).
But even if you don't have that distance, you can do it; it completely depends upon your will and amount of time you're willing to spend with those languages; so I'd like to encourage everyone who has that will and time.
Best wishes to everyone in that process!