additional: You can use (1.)从....中 + verb.... [phrase] 从工作中学习 Cóng gōng zuò zhōng xuéxí [learn From work] (2.)从中 from/ therefrom .....(a story) ..... ， 我从中学习了很多。Wǒ cóng zhōng xué xí le hěn duō [I learned a lot from those/this.] 你可以从中获利 Nǐ kě yǐ cóng zhōng huò lì [You can profit from it] hěn duō很多= a lot/ many xué xí 学习= learn/ study le了 = have PP or past tense. huò lì获利= get some money/ profit.

you can understand it as a collocation in Mandarin, just like those in English, learn from... for example. and here, there is a collocation - cong(从）...... zhong （中）, in this situation, this is equal to from, like learn from, pick from. But!!!!! Though your teacher told you that you can omit the cong , but the nature will be different , and it'd be easily used in an inappropriate way. Of course, native speakers will understand you , just same as when Chinese speaking English to you with errors but you understand them. I am looking for a partner to help each other if you are interested in, let me know. By the way, maybe I can show you more Mandarin knowledge in a logic and proper way.

从错误中学习 cong cuo wu zhong xue xi [learn From mistakes] 从家中出发 cong jia zhong chu fa[go/start From home] 从学生中挑选 cong xue sheng zhong tiao xuan[select From students] 从书中学习 cong shu zhong xue xi[learn From books]