It finally starts to look like a jacket. I have inserted both sleeves and added the facing: 
The sleeve cap is supported by a sleeve head. I used “Watteline” for this. I cut the sleeve head so that it goes from the middle of the front armhole to the middle of the back armhole to give more support, as my fabric is very soft. I still have some puckers at the sleeve. If I would have a wool as fabric you could iron these out, but that did not work here. 
The inner corners of the facing are reinforced with silk Organza. To keep the facing inside I used a pickstich along the edge: 
And this is how it looks from the inside: 
Now I have to decide on the placement of the pockets and the hem.