ISTANBUL American pop star Jennifer Lopez will perform on Tuesday at the Istanbul Festival. Lopez is set to headline the festival at the Yenikapi event area, where special stage setups and increased security measures are in place ahead of her show. The American singer is preparing a visual concept tailored specifically for the Istanbul Festival stage and plans to perform 35 songs during the concert on Aug. 5. She recently performed on July 23 in Antalya on the Turkish Riviera as part of her “Up