As a non-Chinese-speaker/user, who has the most advantage to learn Chinese, quickly acquire it?
Your answer may be Japanese. Most Chinese think Japanese have the advantage to master Chinese fast and well.
I cannot agree. My answer is Vietnamese.
Had you studied Chinese, Japanese, Korean, Vietnamese, you will agree with me.
As a native Chinese user who has been studying English, Japanese, Korean, is good at Japanese, Chinese, English, I studied Vietnamese last year. Before the Vietnamese study, I had the same recognition with other Chinese who think Japanese language is the closest language to Chinese, Japan people write and read same ideograms of Chinese-characters and have the advantage to learn Chinese. There are facts most people may do not know that Japanese, Korean, Vietnamese all adopted Chinese characters (Han-zi, pronunciation in Chinese) as their written language and has been using same vocabulary based on Chinese characters.
Historically, once Chinese created Chinese characters (Han-zi) and related vocabulary, these ideograms were soon circulated to Japan via Korean, and southward to nowadays Vietnam where ancient Chinese occupied till almost AD. 1000.
In Korean, people call the ideograms of Han-zi as Han-za with Korean pronunciation. In Japan, people call them kan-ji with Japanese pronunciation. In Vietnamese, it is pronounced as Hán Vn. Different pronunciations direct to the same ideograms and related vocabulary and has the same meaning. I mean not only the single word of Chinese characters Han-zi, there are a lot of word commonly used these languages and have same pattern and meaning.
For example. the word of water .↓ Chinese, Koran, Japanese sees this sign and reflects the water in mind.
Nowadays, although Korean and Vietnam people do not write the ideograms any more, they can read and understand the meanings like our Chinese and Japanese who use the ideograms everyday. Among Japanese, Korean, Vietnamese, Japanese and Korean are closer to each other grammatically. These two languages are different with Chinese in pronunciation and grammar. Vietnamese is the closest language to Chinese in pronunciation and grammar. For example, Korean and Japanese has no tunes in each syllable as Chinese language has. Common and standard Chinese has 4-5 phonetic tones. Vietnamese has 6 tones and basically covers Chinese phonetic tones.
For a Chinese and a Vietnamese, when they study each other's language, both of them find there are so many similarities in each other's language.
Therefore, Vietnamese has the most advantage to master Chinese and are faster learner than others on the world.