A friend is dating a Nigerian guy and she is learning his language. Do you think she is being stupid and she is wasting her time?

No way, I think that's really sweet!

Is he a General with some type of relationship to a Prince and has come to have access to several million dollars that he needs to "park" in a "safe" account for a short period and for doing so he will commit to giving 25% of the funds... and all he needs is the account number?

No. Because even if they dont work out she will have learned something new. Now if she is solely doing this for him...that is stupid.

Any relationships take time.So the time it takes learning a language shouldnt be that hard.

No, not at all.