Divorce and kids custody

Hello, My name is Sanam Meher ,i am muslim girl from Indore. I have two daughters (4 yr old and 1 yr old). My husband cheated on me when my elder daughter was three yr old. He got married to. a bengali hindu girl and i didnt even know about it. He hide everything from me. I got pregnant again with my younger daughter and he leaved me at my inlaws house and started living with his other wife in a flat. His other wife gave birth to a son. I stayed at my parents house after my delivery. He didnt even talked to me. I went to my in laws house and stayed their few months just to save my marriage but he still didnt talk to me so i moved back to my parents house. Now i wanted to study in australia for my masters .My daughters will live with my parents,but my inlaws are not paying me anything and they are saying that if i will go than they will take my daughters from me. I also wanted to get divorce now. Please help me ,i just have my daughters now.Will they take my daughters from me or will i get my daughters custody.