If you are angry over losing your grandmother, then talk to them about that. let them know that you are still hurt. Take a look at what the arguments are about. be honest and fair. Who starts them? Is someone being unfair, or is it a case of people getting hurt feelings all around? Keep a few things in mind. Most parents want what is best for their children, and they want their kids to be safe and cared for. They might say no to something for a reason that you don't understand, because they have been around longer, and know things that you haven't yet learned. So when you get upset about not being allowed to do a thing, take a look and see if they are simply trying to protect you. Be sure that you do your share at home, and do the best you can in school. respect curfews, and limits. Remember that they are people, too, and that they have bad days, problems with work or friendships, and all the stress that comes from taking care of a family. You have stress as well, getting through school, issues with friends, peer pressure, bullies, whatever is the case in your life. Talk to your parents about those things. Ask their advice. Be willing to really listen if they tell you something you did is wrong or upsetting to them. If the family isn't doing things together, see if you can plan a time at least twice a month for just the family, playing a game, watching a movie, a picnic, anything you can all enjoy. At 12, you are going to have strong emotions over pretty much everything (I remember that age!), and it's easy to get upset or angry. before speaking, take a breath and be sure that you aren't speaking in anger or without respect to your parents. Ask them what they are stressed about, and see what you can do to help.
Truly sorry about your grandmother; not easy to go through. Hugs.