Howdy! I think adding French and Spanish to your repertoire is an ambitious, although attainable, goal. French and Spanish, both being Romance languages, have a lot of overlap in grammar and vocabulary. Mastering the accent in both would take time, but I think it’s quite possible. In my opinion however, Mandarin is a whole different kettle of fish. It does not use the Roman alphabet, the grammar bears no similarity to that of any other language on your list, and it is what’s called a tonal language, which adds a further layer of complexity to speaking. I am a native English speaker, and learned Spanish with some work and time, but did not find it particularly onerous, it was just a skill like any other that could be learned with enough exposure and practice. However, I also learned Japanese. This took many years. A huge hurdle was the writing system, which makes it difficult something as simple as a newspaper even after much practice. And even after years of living in Japan, my linguistic ability is still flawed. So I imagine learning Mandarin might be similar. Not impossible for somebody really motivated and who has a knack for language acquisition such as yourself, and I definitely would never want tell somebody not to learn something they found interesting, but I think having that in the mix increases the time and difficulty by an order of magnitude.

to speak Mandarin you should go to Mandaria yet if you plan to go to China -- should learn Chinese undoubtedly 你的 城市 里 有 孔子学院, 没?