Why are you sitting down to pee? I don't have a good back and can't lift something big.
Bad Back
Explanation
Explain Bear
Okay, so basically, this dude is asking why someone sits down to pee. Then he says it's because he has a bad back and can't lift "something big." He's talking about his pee-pee! I know it's hard for you to understand, but you're not the smartest cookie in the jar.