Did you try inserting an empty magazine and pulling the trigger. The part sticking up looks like the hammer strut. Once the hammer is fully forward, you can lower the strut. The hammer strut has to be in the down position so in can be inserted into the cup on the mainspring housing during reassembly.
This trouble shooting guide "below" may help you.
http://www.guntalk-online.com/2245detailstripping.htm#m3fsreassembly