I think, differences between formal language and informal-daily language make things difficult.

the best advise that I can give is not to be afraid of making mistakes, people understand that learning a new language is difficult so just try and if you get it wrong you get it wrong, also ask people especially native speakers to correct you each time you make a mistake. When it comes to learning vocabulary learn a phrase or sentence of how to use the word instead of just learning the word this will help understand the new vocabulary and help you remember how and when to us it! Good luck everyone

I think pronunciation, listening, vocabulary and I am scared to speak.

Vocabulary. While remembering 5000 most common words isn't an impossible task, dealing with the rest is a difficulty. Whenever I learn a bumblebee I forget a thrush.

Appropriate usage of prepositions come a close second.

The intonation is, according to me, the most difficult. Although someone says something with the correct pronunciation, if the rhythm is not right, people will have trouble understanding.