Your window regulator is jammed.
You will need to remove the door panel and then disconnect the window from the regulator.
You can then push the window to the top, prop it up with something - like a piece of 2 x 3 wood.

This sounds easy in the description but there are D.I.Y.'s to be found on the web.

Common problem with older Benz's.

You don't mention which year or model of car you have.

Ultimately you will need to replace the regulator.

Buy a new one. Pelican has regulators in their catalog. I've also bot them on Ebay. Don't waste your time going to a yard for a used one or you'll probably have the same problem shortly.