Brand Name / Business Name Conflict - competitor copying my API

Sorry for the wall of text. Quick background on my situation — any input appreciated.

competitor copying my API. I've been dealing with this for about 13 months now and the situation isn't improving.

This involves content I created over the past 34 months. I do not have documentation proving my ownership and timeline.

Should I hire a lawyer for this or try to handle it myself?

Not a lawyer or something like that, but I have direct experience with this.

What worked for me was having everything documented. It took 3-6 months but was worth it imo.