I'm very keen to learn Arabic Grammar because I have holidays now (free time )
The benefit of learning Arabic grammer is that you'll be able to properly understand Quran when you recite the words inshallah and you'll appreciate it more. I'm planning to watch a series of lectures on the Medina Arabic book. The course is very popular and a lot of people apparently say that it has really improved their Arabic. The teacher is amazing judging from the lesson I watched.