Mercedes Benz has been using Hirschmann antennas nearly forever. Most cars since 1980 have had electric antennas that are retracted into the car body when not in use. There is a switch on the dash that controls the height of the deployed antennas. Off means it won't deploy at all, the middle position means it will deploy half way (which is often good enough if you don't live in say, Bannockburn) and the full on position deploys the antennas to it's full height.
4 things will stop your antenna from deploying properly assuming your switch is actually letting power get to the electric motor.
Hopefully your problem is the latter point, be before we delve into that, a few words about unbending antennas. It CAN be done of your antenna is just bent and not damaged too badly at the bend. A local stereo installation wizard showed me how one day. It's stupid simple to do ,you just rotate the antenna between your finger and note where it stops being straight and goes all crocked. Once you know where that is, you simply make a large number of very small attempts to bend it back with your forefinger and thumb. You don't want one bend to fix it and besides it's stainless steel and very hard to bend; no, you tweak it a bit till you almost feel it move then back off and check it again. Repeat until done. It may take you 15 minutes to get it right and you will get better with practice. You may or may not get your antenna working and looking right and may be faced with the prospect of replacing the antenna shaft, but sometimes this will work or work well enough.
- The motor could be bad. You need to replace it.
- The antenna may be stripped. You need to replace it.
- The antenna may be bent. You need to replace or unbend it.
- The antenna may be dirty. You need to clean it.
As for cleaning and lubrication of the antenna shaft the tolerances are so tight there is clearance to speak of. The smallest amount of dirt or gunk wan really muck up the works. So, you have to keep it clean and well lubricated. The manufacturer recommends only one thing and they supply one of these with each new antenna. All MB's were delivered, when new with a single Hirschmann antenna cleaning pad and Hirschmann sells more. THAT is what you should use and nothing else and especially not something like WD 40 which gets very gunky and greasy when the solvent evaporates.
The secret is out though, the Hirschmann pads are just silicone just like you'd find in a can of silicone lubricant spray. So you can just get a can of that stuff and spray some onto a piece of paper towel (don't get it anywhere NEAR your paint or chrome) and wipe the antenna with it. Do it a few times and make the antenna go up and down between wipes to loosen any caked on grease. If your antenna is clean, lubricated slightly with silicone and straight, then it will go up and down properly.