YOU SAID:

they said dont bring sand to the beach youll see plenty here

INTO JAPANESE

彼らはここでたくさん見ているビーチに砂を運んではいけないと言った

BACK INTO ENGLISH

They said they should not bring sand to the beach where we are seeing lots here

INTO JAPANESE

彼らは、私たちがここでたくさん見ているビーチに砂を運んではいけないと言いました

BACK INTO ENGLISH

They said they should not bring sand to the beach where we are seeing lots here