The challenges are grammar and speaking (with confidence). Because I studied English at school (always taught confusing grammar without a deeper understanding of usage in a conversation or paragraphs).
And because of that I became shackled, always afraid to speak because my brain had accumulated a lot of grammar (that i don't know which grammar to use).
I can understand if someone speaks English, I can figure out what s/he means. But I don't know the meaning of each vocabulary and I'm always blank and hesitant when I want to answer.