Having the same question I found a good overview here https://chinese.stackexchange.com/questions/1223/how-to-say-cool-in-chinese , hope it helps

酷！kù

There is one transliterated word in Mandarin which is 酷(kù). Just for your information, nowadays on internet, young people tend to use an internet slang “666” which means “amazing” and “fantastic”. 😂

Thanks Fergus

"Cool" meaning "okay, I agree" might be translated "好的“ or ”行“. "That's really cool!" might translate "真好“ or more informally "很棒“ or ”好棒“. And then there are many slang words for cool, which vary in different cultural milieus and location.