Translations:

Teacher -- Sensei, Shishou

Welcome back master! -- Okaeri masutā or Bakkumasutā o kangei shimasu!

May I take your order? -- Watashi wa anata no tame ni sensei ga kakaru koto ga arimasu?

please wait for a while -- Shibaraku omachi kudasai

thank you – arigato

please come back again -- Futatabi modotte kite kudasai.