There are many ways to say this, a lot depends on the situation. "well done" "excellent" "magnificent" "very well done" actually it's easier just to show you a list of what I mean. https://www.easypacelearning.com/all-lessons/english-lessons-level-3/1343-praise-and-encouragement-phrases-you-can-use-to-show-you-appreciate-english-words If you scroll down and read the part where it says "Praising in a classroom" that will give you a better more common list but it is still a long list. What is the situation you were thinking of then the community can give you better answers, although everybody will have their own preference.

Hi, There are quite a few ways to do that. For instance, if someone was a talented guitar player, you could say, "wow, you're really good at guitar!" Or you could say "I'm impressed, you're so talented!" Try to be specific with your compliment and it will be taken as more genuine or real. Instead of "good job," you could say "you did a good job with that presentation, you came across as confident and appeared to really know what you were talking about!"