Astrid,
We Parisians don't have vast wardrobes either, so I don't think for a moment you need worry about not having enough clothes, especially for such a short trip. And Parisian style is not so very different from that of any European capital, including Berlin!!
A couple of pieces of advice, though. If you're planning to sight-see, wear ballet flats for comfort (Paris is hard on the feet, particularly the cobble-stone of the tourist-trail). Open flat sandals are a chic alternative. Most Parisians wear ballet flats for walking, and keep their high-heels in the large totes they always carry, ready to change, if necessary, at work. Oh, and bring a nice pair of oversize sunnies, in Paris they're worn on the dullest of days too, to add a touch of mystique, but also to hide a late-night, or the fact that the wearer hasn't had time to do their famous smokey-eyes!! The three things that are really frowned on here are sports shoes worn in the city (or, indeed anywhere off the running track); sweat-pants and loud printed tee-shirts; and fanny packs. A couple of understated outfits are all you need, with a few accessories to ring the changes. I think you could get away with just two outfits. A well-fitting pair of jeans or linen palazzo pants, ideally, but not necessarily, in white to pair with a Breton top, and a plain, sleeveless shift dress (black or navy if possible) which will take you happily from day to evening if you just vamp it up a bit after dark. AND REMEMBER, in August Paris is virtually empty (they're all down on the Med, soaking up the sun) so you won't find many style police!! LOL!! I'm here, though, so if you'd like to meet send me a PM. I'd love that. Bon Voyage, et bienvenue à Paris!