An honest assessment.
WHEN YOU DO
You serve customers who genuinely do not read your main language You operate in markets with different languages A regulator or client requires it
WHEN YOU DO NOT
You imagine it might help A competitor has one It sounds more professional
WHAT IT COSTS
Translation, initially and for every change Maintenance of every version Testing across versions Complexity in every future decision
THE MAINTENANCE POINT
A second language doubles your content work permanently.
Most abandoned multilingual sites were abandoned because of this.
FOR NIGERIAN BUSINESSES
English serves most commercial audiences here.
Adding Yoruba, Igbo or Hausa versions may serve customers well, and consider whether those customers would read them or prefer English.
Ask your actual customers rather than assuming.
WHAT TO TRY FIRST
Translate one page: the one that matters most.
See whether it produces anything before committing to a whole site.