HI Ibnu,
It might be helpful if you could say which type of films normally appeal to you and also which areas you want to learn, but the below are some of my favourites in any case. Also, just to note some are not fully in Mandarin but are interesting to watch anyway!
Also, just a tip of new to China/Chinese culture, it helps to read a lot about China and Chinese news to gain an understanding of the culture!
<em>Farewell My Concubine (1993) </em>霸王别姬<a href="
https://en.wikipedia.org/wiki/Pinyin" rel="noopener noreferrer" target="_blank"> </a>Bà Wáng Bié Jī - Drama - (set largely during the Cultural Revolution)
<em>To Live (1994) </em>活着 Huózhe - Drama - PRC (set during pre-Communist China to Cultural Revolution)
<em>Black Coal, Thin Ice</em> <em>(2014) </em>白日焰火 Báirì Yànhuǒ - Crime/Thriller
<em>Ash Is Purest White (2018)</em> 江湖儿女 jiānghú érnǚ - Crime/Thriller
<em>If You Are the One</em><em> </em><em>(2008)</em><em> </em>非诚勿扰 <em>Fēichéng Wùrǎo - Drama/Comedy</em>
<em>I am Not Madame Bovary (2016) </em>我不是潘金莲 Wǒ Búshì Pān Jīnlián - Drama