He bought a new car. This is in the past simple tense, and it refers to something that happened in the past. It might be the answer to a question such as 'What did John buy last week?' or 'What did John do with the money he won in the lottery?' He has bought a new car. This is in the present perfect tense. We use this form - in British English in particular - to talk about something which happened in the recent past (or an unfinished time period) which has some influence on the present. You might use this form to explain why John is excited now, or why he has no money now - or maybe why his wife is angry with him now! I'm not sure what your second question is asking - most of it seems to be in Chinese.

This is an answer to your second question - I've just realised what you mean. The issue of whether something happened at a fixed point in the past (eg last week) or in an unfinished period of time (eg this week) is to help you distinguish between the Past Simple and Present Perfect tenses - it has nothing to do with Progressive tenses. This is another distinction entirely. 'This week' is present time - it's the current week that we are in now, so it's fine to use a Present Progressive/Continuous form. You would say 'George works in this office' in the Present Simple - indicating that this is what he usually does. This would contrast with 'George isn't working this week' - a Present Progressive form to describe temporary situation relevant only to this current week. I hope that's clear!