I need to know the meaning of these 2 sentences (song lyrics)

And why they added the suffix "i " to önce and sonra

I know that this suffix is dedicated to the 3rd personal pronoun "O"

Ne senden öncesi
Ne senden sonrası

My Try:

The 3rd person possessive suffix changes the postposition structure into an noun.

Neither the time before you

nor the time after you.

Thank you very much