The two examples you gave are correct. Suppose you want to go to Alexandros’ house, you can say for short:
Θα πάμε στου Αλέξανδρου = We will go to Alexandros’ (home)
Θα πάμε στον Αλέξανδρο = We will go to Alexandros
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.