Hello Joce,
All that should be in the middle of the control is a spring, the connector for the control is part of the top plastic piece, get yourself a new control, it does not have to be a Singer control, all makes are interchangable, YDK is favorite, they don't cost that much, saves a lot of problems.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix sewing machines.