[lugerholsterrepair]

Yes..all true..Look at the right of where the magazine lips/well are and you can see a pretty good run of the hold open and spring. You may be able to see a broken part from there. Either way Tom is correct. Likely what's holding open your bolt is this hold open. Take a thin wooden stick..mayby a popsicle stick or a tongue depressor and push down there. This should release your bolt!
Like Tom indicates..be careful..hold onto the toggles best you can cause when released the toggle/bolt is coming atcha!The stick in the chamber area will help some but it's under considerable pressure.
Let us know how it turns out!