To be frank, do native speakers expect foreign learners to speak and write perfectly idiomatic English? From a native speaker's point of view, English is very easy to learn because everything comes naturally to them, but foreign learners who have little or no opportunity to mix with native users find it incredibly difficult to feel at home with the language. The spelling system is hopelessly complicated and the grammar is a hard nut to crack. When it comes to pronunciation, one is lost in the sea of a multiplicity of accents,from which it is often difficult to choose a good one. Do native speakers think that it is difficult for a foreign learner to master their language?
I never expect someone to speak a second language perfectly, especially if they have not had the opportunity to live in the other country and to mix all day, every day with native speakers.
I agree with bhaisahab that it's always difficult to learn a foreign language but in certain aspects I think English is much more difficult than others (pronunciation and spelling are the main two).