Disaster preparedness

The Federal office of Civil protection suggests that you keep certain items in your house so that you can be prepared in a disaster situation.
Such a situation can easily occur during extreme weather conditions like snow or flooding.
The national emergency number is 112

It is a good idea to install the Nina app (Notfall-Informations- und Nachrichten) from the BKK (Bundesamt für Bevölkerungsschutz und Katastrophenhilfe)

A manual on how to prepare and what to do during a disaster situation can be downloaded in German here, and also in English

A person can manage for three weeks without food but only four days without water or liquids, but what else do you need?
You can download the complete list of suggestions here

Here are some items on the list that they suggest you have in your house

Main Supply for 10 days

Beverages – 2 litre per person per day
Foodstuff: Grain, Cereal products, potatoes, pasta and rice – 3.5 kg of each
Tinned vegetables and legumes – 4 kg
Milk – 2.6 kg
Fat and oils – 0.357 kg
other products you might want like Sugar, honey, dried products like Mash, salt

Medicinal

DIN First aid kit
Pain tablets
Prescribed Medicine
Antiseptic ointment
Flu medicine
Meds for tummy troubles
Tweezer
Thermometer

Hygiene Items

Soap and detergents
Toothbrushes and toothpaste
Toilet paper
Camping toilet
Garbage bags
Household gloves
Disinfectant

Fire prevention

Keep your attic and basement as clean and uncluttered as possible
Fire extinguisher
Smoke detectors ( It is mandatory in most states to have a smoke detector in your bedrooms)
Water bucket
Container for water to use for extinguishing a fire

Power loss – very likely in extreme weather

Candles or tea lights
Matches (Streichhölzer) or fire lighter (Feuerzeug)
Torch with extra batteries
Camping stove with burning fuel
A heater that does not work with electricity, with enough fuel
Having enough cash reserves at home, ATMs work with power.
Charged power/battery banks
The BKK (Federal Office of Civil Protection and Disaster Assistance) has great tips on how to prepare for the loss of power.

Communication

A Battery operated radio with spare batteries, so you can listen to notifications
Battery bank for mobile phones

There are more items on their list like documents and an emergency bag with clothes, blankets etc.

Obligation to assist a person in need

Also, take note that according to Section § 323c of the Criminal Code (Strafgesetzbuch) you are obliged to help a person in need:

(1) Wer bei Unglücksfällen oder gemeiner Gefahr oder Not nicht Hilfe leistet, obwohl dies erforderlich und ihm den Umständen nach zuzumuten, insbesondere ohne erhebliche eigene Gefahr und ohne Verletzung anderer wichtiger Pflichten möglich ist, wird mit Freiheitsstrafe bis zu einem Jahr oder mit Geldstrafe bestraft.

(2) Ebenso wird bestraft, wer in diesen Situationen eine Person behindert, die einem Dritten Hilfe leistet oder leisten will.

Section 323c
Failure to render assistance; obstruction of persons rendering assistance
1. Whoever does not render assistance in the case of an accident or a common danger or emergency although it is necessary and can reasonably be expected under the circumstances, in particular, if it is possible without substantial danger to that person and without breaching other important duties, incurs a penalty of imprisonment for a term not exceeding one year or a fine.
2. Whoever obstructs a person who is rendering or wishes to render assistance to another person in such a situation incurs the same penalty.

You can read more about it here