Welcome to the forum Davor, WW1 is not my area but there are many learned people on here who will help you out. All the best, Leon.
"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
Good close pictures of the inside of the jacket.
Close shots of any markings on the inside would be of great help.
There are a lot of replica uniforms.
I have only one photo of the inside of the jacket and no photo of the inside of Feldmuetze. There is a photo of the button on the pocket.
Pre war Mutz of some type and M-10/14 tunic to me. Hopefully some from the Imperial forum can help with marks and originality. The Lion button looks Bavarian maybe? timothy