How to cut the extended wall layer around opening?

[architekz.188213]

Hi,

If anyone knows how to do explained below, would you please leave your tips in this thread?
My situation is..

1. There is a full height opening on the lower floor.
2. External wall layer of upper wall extended to the ceiling level of ground floor.
3. Problem is, that extended wall layer covers the top part of that opening.

1.png
2.png

Is there any means to cut that extended wall layer around opening?

K.

[antman]

Sometimes joining the two walls will do the trick.