I was trying to say “He made this with all his heart” and then looked for how to say “with all one’s heart” in Chinese. I found a lot of ways to express the sentence but I’m still not sure which one would be the most suitable because there were a lot of words and idioms that appeared:
I’m not sure if native speakers often use those idioms, therefore I’m going to kick both idioms (全心全意 and 真心实意) out of the list, leaving the rest: 真心，认真，and 诚心.
However, 诚心 comes as a noun in the dictionary (even though it also comes as an adjective, but the first word class of 诚心 that appeared was noun and I didn’t see any sentence that used it as an adverb). Leaving only 真心 and 认真. I’m not sure the difference between both words though. Could someone please explain it to me?