Yes they haven't provided API document I don't know why, maybe it's in progress. With only 2 exchanges on Coinmarketcap BFG volume doesn't move at all, is in the range of $50k-70k per 24 hours if it's like this BFG won't get any rank in CMC even though ranking in CMC is important, some people use rankings as a benchmark for the development of crypto projects.
I didn't find any information about API on the Biswap site. So maybe they're still developing it. However, I won't be surprised if BFG's daily volume on the Biswap is the same as on the PancakeSwap. By the way, cryptocurrencies on CMC are ranked by market cap by default, not volume. It means that BFG will be on rank #525 if the Betfury team confirms information about circulating supply.