This is the 2752nd most frequent Russian word.
йенс
The word "йенс" does not exist in standard Russian as a meaningful term; it might be a transliteration or misspelling.
In this sentence, 'йенс' is used as a proper noun, referring to a person's name, Jens.
Йенс купил машину.
Jens bought a car.
Here, 'Йенсу' is the dative case form of the proper noun 'Йенс,' indicating that Jens is the indirect object receiving the information.
Я рассказал всё Йенсу.
I told everything to Jens.
In this clause, 'Йенса' represents the accusative case form of 'Йенс,' showing Jens as the direct object of the action 'видел' (saw).