How I trace a dummy account and file a case against the person behind it

someone has been creating various FAKE FACEBOOK AND TIKTOK ACCOUNTS posting libelous statements about me. These accounts were used to post false remarks, rumors, and accusations about me. Clearly, the same person is doing it, and their only intention is to harass me.

This has been happening aside from private messages since August of 2023. His/her strategy is to add my Facebook friends and make offensive or nasty posts about me in public