Many people in Hong Kong have trouble with English prepositions. Prepositions are those extra grammar words in sentences that tell you things like how, when and where. English teachers like to explain that they make sense and so should be easy. A common example is that we ride 'in a car' not 'on a car'. A horse is ridden 'on' and not 'in'. That sounds easy; we can picture someone sitting on top of a car as wrong and riding in a horse would be uncomfortable.
The problem is that they are not always so easy. We travel 'on' an airplane/ a ship/ a train, but if you picture sitting on top of them it would seem to be wrong. Some prepositions just have to be memorised.
The purpose of language is to communicate and there are times when mistakes cause confusion. Errors that sound silly are bad, but when the meaning has been changed the result can be troublesome. If your boss wants your report in ten minutes, that is very different from wanting it at ten. "At ten", means at ten o'clock.
Hong Kong Chinese People often confuse some prepositions of place for historical reasons. We commonly say that we are going 'to China', when we are already 'in' China. A few years ago it was correct, but no longer. Hong Kong is now in China. When we go home to our flat we can't say we are 'going to Hong Kong' even though our flat is in Hong Kong, because we are also in Hong Kong when we speak. A person going 'to' a place must start from outside that place. This outline should put the problems with prepositions in perspective.