Some people are really good at conversations and they can run a conversation perfectly without having to reach for words. They always find the right words to say in any situation and as a result, people enjoy their conversations. What is that person called in English?
"articulate" is an adjective for those who can express themselves easily, clearly and effectively.
- articulate (adj) expressing oneself readily, clearly, and effectively
Answering the question in the title only- smooth at talking, I would have answered a raconteur.
From Merriam-Webster: : one who excels in telling anecdotes : storyteller
However, extending that to smoothness in dialogue, there are several excellent suggestions above.
And as the OP has highlighted "enjoyment of the conversation," which is not likely to result solely from optimal word choices, but also from the art of delivery, I would say the description that fits is either
a most articulate raconteur, or eloquent conversationalist.
Lucid: Clearly expressed and easy to understand, or (of a person) thinking or speaking clearly.
Example: The drugs she's taking make her drowsy and confused, but there are times when she's quite lucid.
Eloquent: Using language to express ideas or opinions clearly and well, so that they have a strong effect on others.
Example: When required, he could be an eloquent speaker, but preferred talking to small groups.
Fluent: When a person is fluent, they can speak a language easily, well, and quickly
Example: She's fluent in French.