If you rent the place and your landlord doesn’t want it you’re out of luck. If you own the place and your neighbors don’t like the noise of your AC you’re out of luck too. If your building is one of the many buildings protected for historic reasons only God can help you.
European windows don't slide like American ones. They tend to open down the side or at the top, window AC doesn't work. It just leaves Portable AC and people do buy them but they also don't work very well.
