(inb4 dem forum nazis scream at you for not searching)
If your friend's got an older phone that has any sort of lag... he's screwed.
It's described somewhere in this long ass thread
Basically due to crappy programming in Fanta... if your phone lags, your units lose frame rate making them attack slower.
BUT, somehow the enemy movement is not sitting on the same timer and somehow their timer does not slow down from lag, so they're moving at normal speed.
This causes a stupid "glitch" where people with slower phones perform worse in quests... Like not being able to complete Helmut's boot camp... or like how in training events like this current one, a certain unit should get 13 hits in before the boss kills you, but on a crappy phone that same unit gets only 9 hits in.
What you can do though is let him login on your phone and complete the boot camp on your phone.