Looks good! Did you let the boards dry out a bit in the sun before painting to let the moisture escape? See that often where people get lumber and the paint and boards starts to flake/rot early from trapped moisture. Also those floating decks are a dream come true for bunnies/raccoons/possums etc. they will love you!
1) did you prep the ground so nothing sinks? (2) why didn’t you let the wood dry and season for a year before painting? (3) you are going to roast in that greenhouse