* Deal gives Delivery Hero new growth; Europe competition tough. : SEOUL (Reuters) - Germany’s Delivery Hero (DHER.DE) has agreed to buy South Korea’s top food delivery app operator Woowa Brothers for $4 billion and form a joint venture to take on heavyweights like Uber Eats in other fast-growing Asia markets. The deal, announced on Friday by Woowa, is the biggest global play so far for a food delivery app, one of the hottest tech sectors around. Woowa said the sale was “a survival strategy” in an intensely competitive market and also the biggest deal involving a South Korean internet firm.