Step 1
First, on both front and back, raise the shoulder tip by 2-3cm and extend the shoulder line by 5-7cm.
Lower the armpit by 3-5cm and widen the whole jacket by 8-14cm, drawing a straight line as the side seam or flaring it a bit if you prefer this style.
Then, on front move 7-9cm outwards from center for the overlapping, for last draw the collar.