It was the first time I went to this shop/restaurant
初めて行ったお店で牡蠣を食べた
I ate oysters at the restaurant I went for the first time.
初めて – the first time
行った – I went
お店 – shop/restaurant
牡蠣 – oysters
食べた – I ate
もし、「初めて牡蠣を食べた」という風言いなら “I ate oysters for the first time.”
魚介類 – seafood
貝類 – shellfish
日本 
