Hi Oliwia,
"nice" refers to someone or something with a pleasant likeable quality.
Example: nice smile, nice food, nice car, nice weather.
It has a more general usage than "kind"
We use "kind" to refer to someone's character as being compassionate, caring or helpful.
Example:
Kind Judy feeds the stray cats in the neighbourhood every day. / Kindness (noun form) is a virtue.
If you have heard of the phrase "kind samaritan", it refers kindness from one to another total stranger.
Hope this helps.
Cheers, Lance