'It is fun to learn' or 'Learning is fun' would be 'gakushuu WA tanoshii desu' or 'narau no WA tanoshii desu'. In the first sentence 'gakushu' means 'learning by studying', but in the second one 'narau' means 'learning' in general.
Sayonara .
You may say 'oshare' in Japanese; it means "fashionable," "stylish."
No jikan
yoi or ii
If you meant to say "konichiwa" then it means good afternoon/good day in Japanese :L
Sayonara
Ohao Gozaimasu.
yoi shokuyoku
Ohayo (OHIO)
'Kondo' and more usually 'mata kondo' can mean 'next time' in Japanese.
鬼 /o ni/ is a good Japanese equivalent for what you are looking for.
'ii', or 'yoi'.