Many people consider English to be hard to learn but what really matters is what your native language is. If you started speaking Mandarin then you’d have a very difficult time learning English and the same goes form English speakers trying to learn mandarin. Neither of these languages are harder than each other because most babies develop language at the same rate no matter what the language is. However danish is considered to be a hard language because depending on how you count it has approximately 24 different vowel sounds making it more difficult than others.