Aug 12 (Reuters) - German online takeaway food firm Delivery Hero raised its 2021 outlook on Thursday, after more than doubling quarterly revenues, as its fast-growing quick commerce service that aims to deliver goods in as little as 10 to 15 minutes gains traction. It now sees revenues in a range of 6.4 billion to 6.7 billion euros ($7.52-$7.87 billion)for the year compared to earlier expectations of 6.1 billion to 6.6 billion euros. It also now forecasts a negative margin on adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) of minus 2% compared to previously forecast negative 1.5% to 2.0%.