的 uses in a sentence

[Marigrodrigues]

Hello friends, I come to with a grammatical doubth!
what's the grammatical difference between the following sentences? 

I can undestand, but I don't know in which situation should I use each sentece type and where to put 的 properly. 的 really confuses me

 

1. 这是我在北京买的
2. 我看没人看的电影
3. 老师借给我的那本书你看完了

[edelweis]

In these sentences, 的 is used to link a property to a noun.

The property could be an adjective or a phrase, but in all 3 of your sentences it's a phrase.

 

1. the property is 我在北京买, the noun is implicit (it could be 东西)

So the meaning is "things that I bought in Beijing" or "what I bought in Beijing"

2. the property is 没人看, the noun is 电影

So the meaning is "movies that nobody watches"

3. the property is 老师借给我, the noun is 那本书

So the meaning is "the book that (my) teacher lent me"

 

you can read more about this use of 的 here

https://resources.allsetlearning.com/chinese/grammar/Modifying_nouns_with_phrase_%2B_"de"