Girls, help me with advice. My aunt has a big aggressive dog that she …

Girls, help me with advice. My aunt has a big aggressive dog that she leaves to grandma almost every day. Every time I come, it jumps at me (it's sorry). Always tried to turn my back on him. Today grandma asked him to sit at home while she went to the store. He is aggressive and impulsive, on any dog bark he jumps immediately. Today such a situation happened that I lay down (on my back), to the house came grandma and he started running around the bed, jumping on my stomach. I just hope that on the child this did not affect, otherwise if something happened to him (through ultrasound in a week), then he will follow the child. To grandma it's not an option at