JSGME says you have the game installed in "C:\Program Files (x86) \Steam..." etc. Anything installed in a Windows Program Files folder is "protected" and will not take modding. Any mod applied will have all of its cfg and other "system" files rolled back to their previous state. You need to move Silent Hunter out of the program files folder. Consult "
Moving a Steam Installation and Games" on the Steam Support site for some guidance. You can use another hard drive to put a 2nd Steam Library on, or re-install Steam to another folder, and all of the games along with it, or move things "manually", but dependent upon computer system and configuration, it might take a while to accomplish, no matter which way you go.