For Oranguru's "Sage's Riddle" attack, if I put down a Pokemon with more than one type does the opponent have to guess both of its types?
No, they only have to guess one of the Pokemon's types in order to get it right.
Source: Unified Minds FAQ (2019-07-19), TPCi Rules Team (2019-08-01)

Relevant cards

Note: All applicable cards may not be listed below.
SM11_182
SM11_182