Breastfeeding in public is perfectly acceptable in Berlin. It is actively promoted and legally protected.
Rossman pharmacies are the German equivalent to Boots and are found in every area of the city. Here, you will be able to buy nappies, wipes, formula, food, snacks, soothers and everything else you need here. Aptamil and Hipp Organic are available in Berlin although it may taste slightly different to the formula in the UK and Ireland so if you are concerned you should bring your formula from home. Premixed Aptamil is available for younger babies and premixed Hipp Organic formula is also available.
Formula, fresh milk and baby food will also be available in supermarkets such as Lidl, Edeka and Real. You will also find juices, meat, fish, fruit and veg (for cooking) and a variety of snacks, yoghurts, purees and cereals suitable for babies. The tap water in Berlin is safe to drink but might taste different to the water at home so bottled water may be a better option for fussy babies. Evian is widely available and is low in sodium and minerals.