We would recommend you to start learning Mandarin first since it's said to be easier to learn and then build up to Cantonese.
Cantonese is by far the more challenging of the two languages, particularly for a beginning Chinese language learner. This is because there are more tones used in Cantonese (Cantonese uses up to nine tones, whereas Mandarin only uses four).
Given its long history and the isolation of the region in which it is spoken, Wenzhounese is so unusual in its phonology that it has the reputation of being the least comprehensible dialect for an average Mandarin speaker.
Cantonese – Most Difficult Language Overall
Some people debate whether Cantonese deserves recognition as a language in its own right or a dialect of Chinese. Either way, Cantonese poses plenty of problems for students, even if they already speak Mandarin! But why is Cantonese harder than Mandarin for English speakers?
Of all the European languages a native English speaker can learn, Russian is among the most difficult. The Germanic and Romance languages have a lot of the same core because they both have roots in Latin. Russian is from a completely different language branch called the Slavonic branch, which includes Czech and Polish.
Russian is considerably easier than Chinese (any dialect) for an English speaker and likely for anyone who speaks a European language. The Russian alphabet takes a couple of days to learn, and once you learn it the spelling and pronunciation are close to 100% regular.
When linguists rank languages for ease of learning, both Japanese and Mandarin are toward the top (Category 5), especially for native English speakers. However, since you'll be learning a language with brand new sounds and symbols no matter what, they'll both be at about the same level regarding difficulty.
Generally speaking, we might assert that Korean is easier for an English speaker to learn than Mandarin Chinese. But this is very relative. In fact, the US Foreign Service Institute assigns Mandarin Chinese and Korean the same level of difficulty. Both languages are in “Category Four”.
Mandarin Chinese alone is the most widely spoken native language in the world: nearly a billion within China alone and 1.2 billion worldwide—a few hundred million people more than the next most widespread languages, Spanish and English.
The tones are crucial to conveying your meaning. If you decide it makes sense to learn both Mandarin and Cantonese, most people recommend learning Mandarin first before conquering another Chinese dialect. It's interesting that both dialects use pretty much the same characters for writing though.
Despite both being tonal languages, they are not mutually intelligible. This means that while Cantonese speakers would be able to decipher Mandarin writing, they would not be able to understand the spoken language, and vice versa.
Cantonese remains dominant with 96% percent. As for Mandarin, 48% of Hong Kong's population can speak it, compared to 46% of population that can speak English. Previously, English was the second most spoken language.
It takes a learner with average aptitude only 15 weeks to reach level 2 for Spanish or French, but about 50 weeks to reach a similar level of the Chinese language. If you want to be fully fluent in Mandarin, you'd better plan to spend about 230 weeks, which is about 4 years.
Japanese is slightly easier to learn. But, Chinese is much more widely spoken. Both languages have their pros and cons. Ultimately whichever language pulls on your heartstrings the most is the winner.
Comparing learning Thai to other Asian languages
The Thai pronunciation system is similar to Chinese, another tonal language. However, Chinese is easier because it only has 4 tones compared to Thai's 5.
While both languages can be challenging for English speakers, Mandarin is generally seen as being more difficult. This is due to the fact that there are thousands of Chinese characters, while Arabic only includes 28 letters in its alphabet.
Mandarin Chinese
Interestingly, the hardest language to learn is also the most widely spoken native language in the world. Mandarin Chinese is challenging for a number of reasons. First and foremost, the writing system is extremely difficult for English speakers (and anyone else) accustomed to the Latin alphabet.
We drew parallels between Chinese and German, French, Spanish, Italian and even English and we discovered that not only is the pronunciation of Chinese much simpler than French, but its grammar is also more straightforward and easy to learn than German, Spanish, Italian and English.
Though this can provide you with some useful phrases, it will not help you to become fluent. To learn Chinese, you really need to get a good grasp of the grammar principles, so for this reason Duolingo alone will not help you (especially at the higher levels).
It takes about 4-7 years (roughly 2200 to 4000 hours) to become fluent in every aspect of the language, if you spend at least an hour and a half to study every day. However, it's quite common for learners to become more fluent in some areas than others depending on how they allotted their study time.
Although Chinese speakers can read Kanji, understanding spoken Japanese is a different matter. The grammar, vocabulary, and pronunciation of Japanese are quite different from Chinese. For example, Chinese has no equivalent of the Japanese particles “wa” and “ga,” which are essential in Japanese grammar.
Russian is allegedly one of the most complex languages to learn; its Cyrillic alphabet is enough to scare you away. In fact, the Foreign Service Institute classifies it as a category-four language. But don't let that intimidate you. Learning the Russian language is far from impossible.
China has borders close to Russia and has relationships with the countries where the Russian language is the means of communication and therefore the Russian language is considered to be the main foreign language, learned at Chinese universities and secondary schools.
Other languages with non-Latin alphabets, such as Russian and Greek, are also hard for Mandarin speakers. The Cyrillic alphabet that Russian uses can be especially confusing for Chinese learners because it has letters that look similar to English letters, but are pronounced completely differently.