I study, I work and I learn three languaes actively. It all depends on you. I am capable of doing it but I have to admit that the learning process might be a bit slow because I am sharing time with these three ones instead of dedicating one hundred per cent! 

Yea I agree I think it's possible especially if it's an eastern and a western the only hiccup is time. They both require alot of time of you plan to be good at them. 

Chinese and Spanish are two languages very different, i think .So they dont influence reciprocally.

 that's what i thought, i dont know whether it's fit for you ha :p

I thought most polyglots at least START to learn only one language at a time?

Of course it's possible. It's not a big deal. There a lot of people who learn over 5-10 languages at once and they become polyglots.