1. Form and meaning
The genitive often marks possession or a relationship. Masculine and neuter singular nouns commonly use des and an -(e)s ending; feminine and plural forms commonly use der. In standard written German, wegen and trotz are generally used with genitive, although dative occurs in informal speech.
When you study this pattern, identify its communicative purpose first. Then check the verb form, case and word order. German clauses are easier to control when you learn the connector together with the sentence pattern it requires.