1.我一聽到你嘅電話,我就嚟
What does the 聽到 mean here? To “hear” or to “pick up the phone”?
聽到these two words alone mean 'heard'. In this sentence, 我一聽到你嘅電話,我就(趕過)嚟。(After we talked on the phone, I rush here immediately.) 我就(趕過)嚟is the cause, so I assume you have heard your ringtone and have picked up the phone. We talked on the phone, maybe I told you something, and you rushed here asap.
2.
有車嚟啦
“There is a car coming”
what does the 啦 mean?
I know this particle in Mandarin, but it clearly has a different meaning here, because the 啦 in Mandarin makes it past tense + emphasis (啦=了+啊). This sentence is in present tense, so the meaning in Cantonese must be different (and of course Cantonese doesn’t use 了 to indicate past tense anyway). Could somebody please clarify what 啦 means?
Actually you know the answer already! :) In 有車嚟啦(“There is a car coming”), the 啦 makes it present tense + emphasis!
Or you can say 有車啦/架車嚟啦, are more efficient, because you are standing and waiting for a car/a bus, and you see it maybe from a 3-5 seconds distance and you tell your friends 有車啦/架車嚟啦。