I can not seem to wrap my head around this. 

I'm a server at a restaurant movie theater. 

3 small explanations.

Someone lied about me not having a good attitude because I asked them to help stock up our sever station with enough crayons for 140 children and they instead stayed on their phones for the next 10 minutes and then brought in 3 crayons and said oh I thought it would be enough. I asked just three for 140 people,  they shrugged got back on their phone and then I went to get the rest of the crayons and kids menus and they complained to management that I had an attitude and they didn't like my tone. I was written up for my attitude and not being able to work with others. 

Then I had to clean up after 70 people by myself and the person who was supposed to help me decided to look inside, walk away and have a 25min conversation with someone instead of helping me. 
She then walked in after I finished everything, slow clapped and said "Wow, you did it all by yourself, thats amazing". I replied "I dont need a smartass remark, just go make waters or something." She then proceeded to tell management that I was rude and angry and that I was wrong because she didn't mean it that way so I was written up again for my attitude. 

The manager today said that they need me to be positive and that positive me is better than the me who gets angry and frustrated and that I work hard but I need to make sure I stay positive and not to talk to others but instead talk to management when I'm upset. 
I went to speak to management about being upset because a coworker went up to me when I was with a guest with 2 physically and mentally disabled children. While the mother was trying to calm them down my coworker says loudly, "why did you ring this is like this? You're confusing everybody and doing it wrong. Everyone's confused". I asked for someone to bring extra napkins on a water tab. 
I asked the coworker to speak to me out in the hallway and I told her to never do that again it takes away my credibilityand that guest didnt need to have less trust in me that ill do my job while she trying to take care of her children. It was said in a calm stern voice and then she said I was angry and yelling and rude. I was written up. When I spoke to management they said I I'm always misunderstood and that I am not cultivating their positive environment and I got upset and I cut him off mid sentence and said that I was in the right with how I handled the situation and that I shouldn't be punished for advocating for myself. I got written up again for being angry and not being positive. Today was my 3rd warning and my manager said if anyone says anything else again then I'm going to be terminated. 

I'm lost. I'm a hard worker and I should be allowed to speak up if someone else is doing something to me. This is the type of stuff that makes me self harm. I don't know what to do anymore. They have also made it clear that none of them want me there and think it would be better if I was dead by adding a "suicide" button as a drink option as a joke against me. 

I don't know what else to do.