I read Heart of Darkness in high school and I’ll be honest I don’t remember the language of it very well. I don’t remember it being particularly difficult (well, any more than other 18th-19th century works anyway).
What I DO remember is going from having never heard of it before, to suddenly seeing references to it everywhere. It was like a whole new secret code language was unlocked.
It’s pretty short. I would crack a dictionary and maybe read a literary analysis or two and struggle through it. It’s worth it.
This reminds me of that one time in 1st grade I was at the after school program. I had a bit of a cold and started coughing and this girl I was talking to goes “why do you cough like a teacher?” Then, she walked away and never spoke to me again. Same energy. Your friends sound like 8 year olds.