This is the 148th most frequent Polish word.
swojego
"One's own."
'swojego' denotes possession of the dog by Krzysztof, used as a reflexive possessive pronoun.
Krzysztof odnalazł swojego psa w parku.
Krzysztof found his dog in the park.
'swojego' indicates the friend belongs in some way to Ewa, again used reflexively.
Ewa spotkała swojego przyjaciela na przystanku.
Ewa met her friend at the bus stop.
'swojego' shows the possession of the cat by the group 'Oni,' functioning as a reflexive possessive pronoun.