Yes, the Chinese word欣 means happy, but I don’t know whether it can stand alone or not. If you want to learn more Chinese words, you can have a look at
https://www.echineselearning.com/blog/speak-chinese.

It does means happy, but people always use it in some phrases, such as the Chinese words "欣喜 (xīnxǐ) rejoice," "欣欣向荣 (xīnxīnxiàngróng) flourishing," "欣赏 (xīnshǎng) to enjoy," "欣慰 (xīnwèi) be gratified" and so on, so it cannot stand alone. And as to "happy," the Chinese words for it is "快乐 (kuàilè)." Do you have any other questions related to Chinese words? Just feel free to email me at jennifer.zhu@echineselearning.com or you can still ask questions here. I will be glad to help you.-Jennifer

Yes, I agree with Jennifer. The Chinese word “欣” doesn’t stand alone and it is often used together with other Chinese words.

欣 is like gay in English

Meaning joyful, or happy

However, 欣 cannot be used alone as a word,

One may not say [我很欣]
but he may say [我很快樂]

In general, 欣 is used mostly in name of a person,
and occationally in those 4-word idioms.