You don't necessarily need 10x effort (depending on your definition of "effort").

I'm a Hongkonger. I had lived in Montreal since I was 10 until I finished my bachelor's degree.

I didn't really do Saturday schools. I tried that for one or two years but those really had no effect on my proficiency in Chinese.

Yet, I can confidently say that I'm fluent in four languages, if you count Mandarin and Cantonese as separate languages.

What you really need is motivation and environment.

For me, I was motivated to become good in English and French because I found Québécoises girls really attractive, so I naturally paid attention in English and French classes. I also had the environment because I was introduced, by my cousin, to play with Québécois kids early on in elementary school. I simply did not stick with other Hongkonger kids.

I also liked Chinese literature like Romance of the Three Kingdoms and Jinyong's wuxia novels. So I just grabbed a Chinese dictionary and continued to learn Chinese on my own. I liked watching imperial court drama produced in Mainland China, so I watched a lot and learned my Mandarin accent that way. I don't regard that as "spending effort".

I still spoke Cantonese with my family so I got my mother tongue covered. Again, that's not effort.