It's no easy in German, Italian, Spanish , French - all have a fixed response - bitte schon, prego, de nada , de rien. Sounds nice but just as meaningless - a pleasantly. We have to stumble around finding something and it chsnges over time. Some staff are trained in a certsin way, some are free to say what they feel is OK. I thought what do I say if I'm thanked - well context is everything but I have a range of phrases- it's a pleasure, glad I could help, you're very welcome , no problem , anything else I can do. What do you say when thanked? Nothing?