java commands arent working after following a tutorial
Take a closer look at this section:
...CustomModelData:123456,Lee Enfield:1b,Enchantments:...
Lee Enfield, I presume, is a custom tag you're using to detect that item. Tag names cannot contain spaces in commands, while the files technically allow for it, Minecraft won't allow it. So you should change your tag name to something without spaces: LeeEnfield
That seems to be all, the command is marked correct when the space is removed.