hi im trying to use follow me, and this is what happened.
how to avoid like the red circle?
What are you modeling? The blue faces are inside out due to your modeling process. Is the angled piece supposed to be seaprate from the vertical one? In general you would need to extrude the angle part past the vertical face and then remove the waste. One way to do that would be to trace the vertical edge on the face of the angled part and then use Push/Pull to push away the waste.