Many happy returns (of the day)

(А)Happy birthday! - more common, especially in informal situ­ations.

Congratulations may be used when someone comes of age (достичь совершеннолетия)

eg Congratulations on your coming-of-age.

Otherwise it is practically never used as a birthday greeting nowadays.

The answer to all these is "Thank you".

Now here are some other wishes for various occasions (случаев):

Have a good/nice holiday - to someone going away on holiday. Note that "holiday" here means отпуск.

Reply: Thank you/Thanks (I’m sure I/we shall).

Have a good/nice weekend. - to one’s colleagues before leaving work on Friday evening.

Reply: Thank you. (You too).

Have a good/nice time to someone who is going to a party or

Enjoy yourselfentertainment (развлечение)

Reply: Thank you (I’m sure I shall.)

Have a good journey. - to someone about to travel somewhere, but not usually when he is going on holiday (Here "Have a good holiday" is more usual).

Reply: Thank you/Thanks.

Good Luck!to someone about to take an exam,

The best of luck!go for interview, etc.

The person addressed replies "Thank you" and may add "I shall need it".

All the best. - to someone who is leaving for a long time, or before an examination, interview, etc.

I hope you’ll soon be better. - to someone who is ill.

Note that there is no wish in English corresponding to the Russian Приятного аппетита!