Where do I learn Marathi for my gf?

Hey non Marathi from Bangalore, sorry for intruding. My (19m) gf(19f) is Marathi and we both live in Bangalore, and my mother tongue isn't Marathi and for her birthday, I thought It'd be a nice surprise to randomly start talking to her in Marathi. Where should one go to learn Marathi? And I was told that her Marathi is Bangalore Marathi and it's kinda different from the Marathi they speak in Maharashtra. Can you please let me know where to learn Marathi? Thank you!