There is a small pin on the block under the barrel that holds the extractor in. Take this pin out (with a small punch) you will be able to slide the whole extractor out of that block. Be careful sliding it out because on top (barrel is the top) of this extractor is a very small piece of bent metal (bent like a smile) and this gives tension to the extractor.
You can bend this slightly to increase or decrease the pressure on the extractor. Your problem sounds like there isn't enough pressure.
If there is too much tension from the spring, the extractor will press into the cartridge with too much pressure and it will pull the cartridge out of the chamber, but then take some effort to pull the cartridge free from the extractor.