Howdy Futo333 and Gygoracdes,
Thank you for reporting this issue of low fps. Are you both using a heavy amount of BSP brushes? BSP brushes are going to lower you fps significantly on a mobile device. We are still currently in the optimizing stages for mobile devices with UE4. BSP brushes are included in that optimization. How you been able to see any significant changes when not using BSPs?
Thanks and have a great day!