I learnt Arabic myself, ( it was difficult, very difficult at the beginning )  I'll tell you the most difficult part through the whole process is knowing how to write. It also matters if you are approaching the language correctly or not, Arabic is different from all the languages out there. Reading could be difficult at times for beginners. When you start applying to it things like "Aldmh" and "alksra" ( grammar stuff) because that will change the pronunciation in standard Arabic. I don't think pronunciation is hard because there's a trick to it all, and once you discover it, things will get easier with practice. Writing in Arabic is sort of connected with the way you pronounce words. If you are learning dialects, this will make it 10X harder.Some Arabs write words with their dialects. Standard has become like the "professional" language, usually used with news articles , podcasts, work  emails, schools, etc. Now, I speak the language fluently with perfect accent and I know several dialects, those I can speak fluently with them too. 

Try to learn standard Arabic first then choose dialect and that would be easier 

Learning vocabulary! Nothing ressembles to anything I know.