MCPE stuck on white screen or on "Generating terrain" screen on iPa Air2

Since I have switched to iPad Air 2 MCPE gets always stuck at the white screen right after the Mojang screen. Or if it moves past that it is really really slow and it gets stuck at the "Generating terrain" screen, both in single and multiplayer. Also, right after the Mojang screen it gives a beeping sound, like an error message or something similar. Any ideas?