Karen R. answered 06/04/19
Experienced Tutor, Duke Senior, Specializing in Learning Needs
As a linguist, I can tell you that the perceived difficulty of a language really depends on a person's first language(s) -- which language(s) you learned first in your childhood. If your first language was Cantonese or Russian, you may have more difficulty learning English grammar and pronunciation than someone whose first language was Dutch, Italian, or French. This is because languages like Dutch, French, and Italian are much more similar to English in terms of grammar (how sounds are put together to form words that makes sense, and how words are put together to make sentences that make sense) and pronunciation (how you actually make those sounds with your mouth, throat, and nose) when compared to languages like Russian or Cantonese.
This is because English is a language with Germanic, French, and Romantic roots, plus a couple other smaller influences, so speakers of other languages within those languages (like French) or language groups (like Dutch, which is Germanic, and Italian, which is Romantic) will have a much easier time learning English than speakers of languages in farther-away language groups, like Slavic and Sino-Tibetan languages (like Russian and Cantonese).
However, the reason why most people (even first-language speakers of English!) find English confusing is because of its often-conflicting grammar rules. This is a result of many things, including the fact that Old English was greatly influenced by French grammar rules during (and after) the Norman conquest of the Anglo-Saxons in 1066. This essentially made French grammar fight over sentences with Germanic grammar, settling on the grammar that English currently has, where most of our words and sentences are made based on either or both of these sets of grammar rules.
Other confusing aspects of the English language come from the simple fact that LOTS of languages have influenced English over the centuries, including Arabic, Greek, Spanish, Latin, and the hundreds of indigenous languages that existed and still exist on American soil. And don't forget the fact that there are four major regions on the planet (the Americas, Western Europe, Africa, and Oceania) in which local people have semi-independently developed hundreds of dialects, many of which are actually mutually unintelligible! For example, if I put someone from a small town in Kenya (where Swahili and English are the official languages) in the same room as someone from a small town in Ireland (where they may speak Irish alongside English), these two people would have a pretty hard time understanding each other! Yet, they would both speak English.
This brings me to the last major reason why people find it hard to learn English -- it's often taught incorrectly. Aside from the leagues of teachers who never actually learned how to teach languages effectively (which is such a huge problem, I could write a book on it), making the whole exercise more difficult than it ever needed to be, many English teachers teach their students "formal English," which is rarely ever used in real, day-to-day situations. We don't speak the way we write an English paper, yet so many students around the world are taught that way -- which includes memorizing much more difficult grammar rules! Since informal English is much more simplified (grammatically and phonetically), these students get a nasty surprise when they find they cannot understand the way native speakers form basic sentences or sometimes even how they pronounce words.
But it does not have to be that difficult. Learning English (and really, any language) can be easy! All it takes is a good instructor who understands how human brains naturally acquire languages and who is willing to put in the time necessary to help you learn.
Don't hesitate to reach out and let me know if I can help in any other way!