去台灣讀外語系(英文)之後就返返黎香港讀法律

Well, it is good to have plan for study but you should find out whether what is the requirement for School of Law in HK, do they accept the credit that you are going to take the course in Taiwan, as I know they will be count because Taiwan academic credit is not recognized by CommonWealth countries. Make sure you asked before you are going to do, good luck.