2900 Euro spendable income is 90% of the average family income in Berlin (source in German). And your family's earning potential is higher than your starting salary, as you could hope for a raise, or your wife could also start working, at least part time.
You won't be able to have a very lavish lifestyle, in the sense that many people you see will have something you cannot afford, for example a new car. But before you get jealous, you have to remember that those people have given up something else you are spending money on to get that car. It is only the rich ones who can have all signs of affluence at once.
With that kind of money, you won't be starting at the bottom of the social ladder. You may not be able to afford everything you see advertised, and you will probably live in a flat smaller and further away from the center than you wish (rent is currently really expensive in Germany), but many people you interact with on a daily basis will be living on less.
