Sure: the point is that every language has its own set of difficulties and hurdles, and your existing knowledge of other languages may remove or lessen some of those hurdles. So a Farsi speaker will not need to learn the Arabic alphabet from scratch, but (other than loanwords) the languages' vocabularies are different. On the other hand, a Maltese speaker will need to learn the Arabic alphabet, but will find Arabic vocabulary familiar as both Maltese and Arabic are Semitic languages.