As God says, take handle off and first make sure the spindle hasn't slid out of the back of the handle, this would just cause the handle to spin, if thats ok then it looks like you'll need a new espag.
If you have an identical window, fitted at the same time as your broken one then just take your measurements of that espag and order online, you'll also get an idea which way all the mushrooms slide, this will help you when trying to open your jammed one, sometimes you can use one of those flexible steel spatulars from out your kitchen draw, slide it in and then push or pull it sideways, if the opener has shootbolts in each corner then you'll need to remove the glass, this will help when levering the opener about to disengage them without fear of breaking the glass.
Can be hard but some can be a doddle to open