[Closed] no idea what was correct here

Better fold after the flop raise. You are beaten by a lot of hands (9, almost any pocket) and even a flush draw has excellent equity against you (14 outs). The pot isn't that big.

imo betting the flop is not a good idea. why bet the flop?

The board texture is favorable. One player checked already, so he hast not much. Well he could slow play, but he has the 9 not very often. 2 players behind hero remain, but there are only 4 cards left that could have hit the flop and very likely only 2 cards have the better hand because hero has a very good kicker. Hero should have the best hand quite often and he has to protect it. Almost any card on the turn will be higher than the 3, so hero can't play well on the turn against 3 opponents. Fortunately hero can get the opponents to fold often because the two 9s are frightening.

There is a certain risk someone has a better hand or a flush draw which could raise, but the probability of it (or better the lack of) are worth the risk.