Learn Four Cases in German

The concept of cases is foreign to English speakers because we don't use cases quite often in our language. A case simply means that you mark or change a noun in some way to show what it's doing in a sentence. Cases aren't used sometimes in English, but they're necessary for German. In English, we use word order to show who is doing what to whom. If we change the order of the words, we get a completely different meaning. That’s because word order matters in English.
In German, word order is much more flexible than in English. And in longer sentences, sentence parts can start moving around in strange ways. 
The case of a noun indicates the noun's purpose in the sentence as well as its connection to the other nouns in the phrase. In German, cases are so important. You can figure out who the subject and object are in a sentence by looking at the words in front of the noun. To put it another way, who is doing what to whom in a sentence. 
There are four cases in German that you will have to learn them.

When you use a noun, it is given a case. The words that go with the noun have the same case as the noun. Cases for articles, nouns, pronouns, and adjectives must all be the same.

The function of the noun in the sentence, the specific verbs used in the sentence, and the particular prepositions used throughout the noun are usually the determining factors. When you're familiar with the changes of the definite “der, die, das” and indefinite articles, it's simpler to choose the correct case “ein, eine, ein.” Personal pronouns change in the same way that definite and indefinite articles do. This is also the case in English, where "I" becomes "me" or "my."

The noun's base form is the nominative case and it indicates the sentence's subject: the person or thing that does the action. It's also the word that explains how to combine a verb. The noun's case and gender must be matched by the article. 
The following are the questions for the nominative case:

1. Wer? - Who?
2. Was? - What?
The nominative case is used after the verbs:
3. sein – to be
4. werden – to become
5. heißen - to be called
The definite article and the indefinite article remain the same and do not change in the nominative case:
6. die Farbe – colour
7. die Stadt – town
8. der Schüler – pupil
9. der Turm – tower
10. das Foto – photo
11. das Rathaus – town hall

The direct object is another name for the accusative case. The thing that is decided to act upon is the direct object. After certain verbs and prepositions, we always use the accusative case. The masculine words, i.e. the der words, are the only words that modify their structure in the accusative case. The other cases are identical to the nominative case. The following are the questions for the accusative case:
1. Wen?- Who?/Whom?
2. Was?- What?

The article has to match the case and the gender of the noun.
1. Masculine form in the accusative- the man
2. Feminine form in the accusative- the woman
3. Neuter form in the accusative- the apple
4. Plural form in the accusative- the balls

The accusative case used after certain prepositions are:
1. bis – until
2. durch – through
3. entlang – along
4. für – for
5. gegen – against
6. ohne – without
7. um – around

The indirect object is also known as the dative case. The indirect object is the noun that accepts something, which is generally the direct object in the accusative case. The dative case is also used after certain verbs and prepositions. The dative case's question is:
1. Wem? - To whom? 
2. Was? - What? 
3. Wer? – Who

With the dative, there are a few verbs that are always used. The most widely known ones are listed below.
4. danken – to thank - to give thanks to
5. folgen – to follow
6. glauben – to believe - to give belief to
7. helfen – to help - to give help to


The case and gender of the noun must be matched in the article.
8. Masculine- dem- einem/keinem
9. Feminine- der- einer/keiner
10. Neuter- dem- einem/keinem
11. Plural- den- keinen

Some German verbs take the dative case. 
12. antworten - to answer
13. danken - to thank
14. glauben - to believe
15. erzählen – to explain 
16. helfen - to help
17. gehören - belong to 
18. gefallen - to like
19. geben - to give
20. schenken – to give present

The genitive case expresses ownership or possession. It is used in the construction of noun belongings. After certain verbs, prepositions, and adjectives, the genitive is also used.
The question for the genitive case is:
1. Wessen? - Whose?
The article has to match the case and the gender of the noun.
2. die Schwester - the sister
3. die Farbe – the color
4. das Jahr – the year
5. das Model – the model

The following are the most common prepositions preceded by the genitive:
7. wegen – because of
8. trotz – in spite of
9. während – during
10. außerhalb – outside
11. innerhalb – inside