What's the most difficult thing you've ever had to learn in English? For me, even as a native speaker and English teacher of many years it would have to be spelling. For some words there really is no logic! 

When the English tongue we speak.

Why is break not rhymed with freak?

Will you tell me why it's true

We say sew but likewise few?

And the maker of the verse,

Cannot rhyme his horse with worse?

Beard is not the same as heard

Cord is different from word.

Cow is cow but low is low

Shoe is never rhymed with foe.

Think of hose, dose,and lose

And think of goose and yet with choose

Think of comb, tomb and bomb,

Doll and roll or home and some.

Since pay is rhymed with say

Why not paid with said I pray?

Think of blood, food and good.

Mould is not pronounced like could.

Wherefore done, but gone and lone -

Is there any reason known?

To sum up all, it seems to me

Sound and letters don't agree.