I'm sorry, you've made two mistakes. I learnt Italian in Italy for one year, so you can trust me.
1. I miss you:
Mi manchi/ or Tu manchi a me.
"chi" pronounced "ki", the tense of the word 'miss' in italian refers to the object instead of the subject.
2. 祝你係香港有個開心既旅程
Ti auguro un buon viaggio a Hong Kong!
3.好開心可以識到你
Piacere di averti conosciuto!
1. Io manco te.
2. Ti auguro un viaggio felice nella Hong Kong.
3. Piacere di conoscerti.
(1. Io = I, manco = I miss, te = you)
(2. auguro = I wish, un viaggio= a journey, felice = happy, nella = in the)
(3. piacere = a pleasure, di = of, conoscerti = know you)
Italians all learn English in school. But their English levels are generally poor. If the person is well-educated, he/she should understand English just fine.