First Practice Sentences

我的家有四口人。

2. 作天是三月二十五号. 

Good!

3. 我去超市中午十二点.

我中午十二点要去超市。

In Mandarin, you always indicate the time and place before the action. In this case "going to the supermarket" is the action. So you would say the time, and then what you're doing. And then the "要" is just to signify that you're going to go, that it's in the future.

4. 我有一杯咖啡和烤面包.

This sentence makes sense, but it means "I have a cup of coffee and toast". 

You could say "我喝了一杯咖啡，吃了一片烤面包" which means "I drank a cup of coffee, and ate a piece of toast."

5. 明天是复活节.

Good!

6.我看了一部电影由贾樟柯.

Assuming you want to say "I watched one of 贾樟柯's movies", it would be:

我看了一部贾樟柯的电影。

Or "我看了一部贾樟柯导演的电影", which means "I watched a movie directed by 贾樟柯."

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I should mention, I'm not a native speaker, but I'm pretty confident in these corrections as the sentences are quite simple. :-) 

加油～