SHENZHEN, China—Wu Lei says his small construction company in central China has accepted commercial paper from property developer Evergrande as payment for two years but with that paper’s value now in doubt, his firm is on the verge of collapse. China Evergrande Group, saddled with more than $300 billion in total liabilities equivalent to 2 percent of China’s GDP, is in the throes of a liquidity crisis that has it scrambling to raise funds to pay its many lenders and suppliers. Wu, 35, was one of around a hundred protesters who descended on the headquarters of the country’s No. 2 real estate developer in Shenzhen this week desperately seeking assurances of payment. “We were working for Evergrande, so our suppliers trusted us with the materials without us paying upfront. Now they’re suing me, courts have frozen my property and I’ve sold my car. And I still have employees who need …