It's hard to say whether we are good friends or not, but I had a lot of fun!
It's hard to say whether we are good friends or not, but I had a lot of fun!
It's hard to say = 言いづらい（わからない）
whether or not = かどうか
we are good friends = 私達はいい友達（仲がいい）
but = でも・けど
have (a lot of) fun = （すごく）楽しむ
had＝haveの過去形
I had a lot of fun = すごく楽しかった
I don't know if I would say we're best friends or not, but we all had a good time the other day.
この場合、次のような言い方ができますよ。
ーI don't know if I would say we're best friends or not, but we all had a good time the other day.
「私たちはすごく仲が良いのか悪いのかわからないけど、この前はすごく楽しかった」
we all had a good time で「みんな楽しい時を過ごした」＝「楽しかった」と言えます。
ご参考まで！
アメリカ合衆国 
カナダ 
