(Hello, I tried doing small edits and getting rid of unneeded things. However, this is really good. As for advice, consider adding sentences because it would sound more natural. Also, in written English, there is usually only one "and" in a sentence. It did not let me post on the "corrections" section so I'm posting here.)

My first writing assignment Hello Lisa, My name is Magali, I’m from Argentina. I’m writing to you as part of the link up project. I live in Resistencia with my older sister and her son. I love travelling everywhere on my bike, playing volleyball and the guitar. I’m not that good at playing the guitar but I enjoy learning it. What I like the most is spending time with my family. In this letter, I attached a photo of my mother, sisters, nieces and I on our New Year’s Eve party. I’m the one in the red dress. The dark-haired girl on my right is my oldest sister Julia. She’s very modest and sensitive. The one on my left is my mom. Besides her is my other sister Gabriela, she’s very easy-going and she’s got a good sense of humor. In front of her is my niece, Victoria, she loves dancing. Next to her is my youngest niece Agustina, she’s wearing a beautiful white dress. In the left-hand corner is my oldest niece Merlina. She’s stunning, has lovely sun-tanned skin, and long, straight hair. Please email me back and send me a photo of you and your family or friends, and tell me about them. Bye for now, Magali This is a famous Argentinian singer. Her name is Marilina Bertoldi. She’s middle aged, slim and sun-tanned. She has short and wavy dark hair. She is also green-eyed. She’s attractive and in this picture she looks stunning. She seems relaxed and nice, easy-going and determined. She looks as if she’s a model or a professional designer. Watching interviews and listening to her songs, I can tell she’s very assertive and clever but also sensitive and emotional. She seems really confident because she’s always making eye contact and talks proudly about all that she has achieved in her life. She always wears stylish clothes but she has her own style. In this photo, she’s wearing red pants and a white shirt.