The Foreign Service Institute of the US Department of State expects you will reach “General Professional Proficiency” in Chinese (either Mandarin or Cantonese) in 88 weeks, or 2200 class-hours.
Both are classified as Category IV languages, along with Arabic, Korean, and Japanese.
Category III languages (Thai, Ukrainian, Icelandic, etc.) are expected to take 1100 hours to reach a similar level of proficiency. Category II languages (German, Indonesian, Malay, etc.) are 900 hours, and Category I languages (Dutch, Norwegian, Swedish, etc.) 600–750 class hours.
They’ve been doing language instruction for motivated adults for 76 years. I doubt there’s a method out there that’s going to be significantly faster.