Can anybody help me?
Nobody can help you but the exchange.
They told me it would take one month before we can withdraw the coins, but the wallet is still in maintenance.
You have to be patient. If they told you to wait for such a long time, it could be an issue they have hard time solving. Sometimes exchanges need help of the coin developers, so it takes time.
I just want to take my coins out of my wallet, but I think they are stuck there for ever.
Well, the risk is always there. I don't want to give you false hope, but I once waited for a couple of months before I was able to withdraw my coins (it was another exchange though and a different coin).