通常語法是learn by doing sth,
還有就是learn...by oneself(自學)
earn from是從……得知,向……學習,是指從某個地方或者人學到知識
通常語法是learn from sb向某人學習
短語
learn French from him 向他學習法語
learn English from me 向我學英語
learn lessons from mistakes 從錯誤中吸取教訓
learn off 記牢,背熟