This post will focus on how hard it is to learn Persian if you are an English language speaker.
Persian is easier to learn than its reputation, as some say this is a difficult language to learn. In truth, it’s difficulty is only average, and it is one of the easier IE languages to learn. On the plus side, Persian has a very simple grammar and it is quite regular. It has no grammatical gender, no case, no articles, and adjectives never change form. Its noun system is as easy as that of English. The verbal system is a bit harder than English’s, but it is still much easier than that of even the Romance languages. The phonology is very simple.
On the down side, you will have to learn Arabic script. There are many lexical borrowings from Arabic which have no semantic equivalents in Persian.
English: two (native English word) ~ double (Latin borrowing)
Note the semantic transparency in the Latin borrowing.
Persian: do (native Persian word) ~ tasneyat (Arabic borrowing)
Note the utter lack of semantic correlation in the Arabic borrowing.
Some morphology was borrowed as well:
ketāb – book
kotobxānah – library (has an Arabic broken plural)
It is a quite easy language to learn at the entry level, but it is much harder to learn at the advanced level, say Sufi poetry, due to difficulty in untangling subtleties of meaning.
Persian gets a 3 rating as average difficulty.