If you are legit 12 years old then another thing I can suggest is just telling yourself you're great. Appreciating yourself. Stop thinking about everything you can't do, think about what you CAN do.
It's a struggle, but just gotta keep it up dude. Don't focus on your failures, focus on your accomplishments. Focus on the positive small things even, they matter too. Like beating a video game, or having a convo. These are all good things that we miss not realizing.
First you need to accept that life is fundamentally meaningless, that there is no inherent purpose to your or any one else's existence. Read into topics like astronomy, abiogenesis, and the geologic timescale of earth. Read "the Selfish Gene" by Richard Dawkins. Once you've removed your humanity, then you can begin to develop you're own values system.