You need to look at the Visa Bulletin - https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2026/visa-bulletin-for-april-2026.html It's released monthly.
Currently those who applied under F1 in May 2017 are just now becoming eligible for visas, and those who applied under F3 in Dec 2011 are too. You can't really guess your wait based on that, as it can speed up or slow down in either category, but it'll give you a rough idea at least.
If you are asking about divorce to try and skip the F3 line and move to F1, remember that will only work if you do actually want to divorce your spouse. You can't divorce them, get a visa, and then re-marry them.
Also bear in mind that Nigerians can't get visas now anyway.