I would like to know how you learn two languages at the same time?
I got a solid foundation in Spanish, and then I started learning French for Spanish speakers. It helps having a good head start in one language before you take on a second. I like learning French for Spanish speakers because it allows me to practice both languages at once, but it would be impossible if my Spanish weren't already fairly strong (about B1).
I have read that it helps to separate your studies. I tend to do French in the morning and Spanish at night. Others have said they do one language in the living room and another in the bedroom or kitchen or whatever.
It also helps if you study two dissimilar languages. You're probably okay with German and Spanish, but French and Spanish would be really tough. Russian, Korean, or something with a totally different letter set would probably not be too confusing alongside a latin based language.
I was leveling up in both Spanish and English at the same time, but I have started focusing more on Spanish. I did review some French last night, and read up on its grammar, but I won't seriously go back to French until I finish my Spanish tree (about 21 more skills).