as noted in the prior posts, lifestyle it the most important issue when getting a dog so that it shares your life not just lives in your world.
I have noted a couple sites that may help you better understand breeds that generally do well in apts/flats.
Small dog breeds make great apartment pets.
Top Dog Breeds for Apartment Life
this should help.
One thing to note, many of the sites that discuss breeds suitable for apts living in fact cover breeds that do not do well in apts. A 20 year study showed that the Miniature Pinscher is rated the 3rd worst breed for apt life. This is something I have know long before that. Many assume just because a dog is small in weight this makes it suitable for an apt/flat. There is nothing further from the truth. Fact is a Greyhound is a great apt dog and is one of the ultimate couch potato's. It is quiet on average and reserved when in doors where Miniature Pinschers are in fact terriers, older than the Parson John Russell Terrier (the JRT) and older than the American Rat Terrier. These dogs are high energy and need a yard and a great deal of time off leash in an enclosed secure space to wear off energy. In addition many sites say that terriers are good apt dogs but fact is terriers are guard oriented quite often and therefore will bark at noises.
Hopefully these sites can help you get an understanding. If you see ones you like than research specifically these breeds to see what it will take to have one in your home as far as energy level and lifestyle.
good luck.
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No I am not a Miniature Doberman, I was around 200 years before Karl Frederich Louis Doberman created the Dobie, and as for my friends the Manx cats, yes they are better at playing fetch than I am, I am a Miniature Pinscher.
http://blackhawkkennels.webs.com/