We learnt English words with transcriptions at school. English spelling was really frustraiting to me. I had to repeate many times "андэстэнд - ундерстанд" to remember the word "understand". Learning vocabulary was the most difficult part of learning English. Pronunciation seemed impossible to me at first, but then I started getting used to it.
Articles were just useless, meaningless words, which are put before nouns without any rule. Several years had passed before I started understand what they are needed for.
The Continious aspect was easy to grasp, but the Perfect took a lot of time. Many constructions were easy to remember but looked very strange: "I'm ten years old" (what is "old" in this sentence and how is it connected with other words?), "I'm cold" (the enviroment is cold, actually), "I was given a pen" (Who was given: I or a pen?). Another problem was conversion (when a noun becomes an adjective or a verb or vice-versa). If "summer" means "лето", then what does "summer holiday" mean? "лето каникулы"? But another problem appeared when Ihad got used to conversion: where are its limits? Why "North Pole", but not "Nothern Pole"? What's the difference between "magic" and "magical"?
Questions and indirect speech were easy for me to understand. I did not have serious problems with "there is/ there are, verb s to and to have" at the beginning. Modal verbs have been impossible to master by now, I keep forgetting them. It always takes time to remember where to use an infinitive with "to", a gerund or an infinitive without "to". Prepositions have always been difficult. Pobably those who learn Russian have similar problems with this part of speech. I thougt: "what is "at", where is it?". The lack of distinction between transitive, intransitive and reflexive verbs was also confusing.