There are three main ethnic groups in Nigeria, the Igbo, Yoruba and Hausa, and I happen to be from the Igbo tribe but I've lived most of my life amongst the Yoruba people. I remember my dad used to tease me back in the day because I didn't know how to speak the Yoruba language even though I had lived there for more than ten years.
Although he had a point, I believed that the only reason why I didn't know the language was because I wasn't paying attention to it, I didn't know I had to learn it until he began teasing me about it, that was when I decided to take it serious, probably too serious. I remember how I would go to my Yoruba friends with a book and a pen in my hand, asking them to translate certain words from English to Yoruba so that I could write it down.
I was making progress and was beginning to use some of those words that I had learnt on street sellers and some friends around, but just when I was beginning to make some real progress, we moved out of the area and I left all of my friends behind, even the one who were coaching on learning the language. Unfortunately, I didn't make any new friends where we moved to and nine years later, my Yoruba still sucks but at least I tend to understand a bit of it and could engage in minimum conversations with people, as long as I speak in English while they reply in Yoruba.
I probably didn't understand the importance and benefits of learning a second language until I left home for the east, a place where majority of the people here speak the Igbo language (because the East is an Igbo land) and the few Yorubas and Hausas around tend to value any and everyone who can speak their language fluently especially if you're not from their tribe.
I remember the one time I and some of my friends had an issue with our industrial training logbook, we were all forced to go through extreme measures to rectify that problem, all of us except for one. This guy and his family had lived in the north all their lives and he knew the language so well, it didn't even sound like a second language when he speaks it.
Of course none of us could complain about the man being partial, there was no one to complain to because he was the boss. But if there was one thing I learnt that day though, it is how powerful language can be, and living in a country like Nigeria with over 525 native languages (according to Google search), I think it's only fair and wise when I say that we should learn at least three of those languages.
Same thing applies to international languages too, if you have the time, do learn how to speak as many languages as possible.. I'm sure it will come in handy in the future.