This sentence is incorrect. I am not sure what you mean by "alone with" but the use here is not right. You would have to say " he learnt the language only from me" if you mean you were his only teacher, his only means of learning the language. " alone with" means you are together with just one other person.. for example "at last my mother left me alone with my friend". It means you and your friend were in a room with no other person present. I hope this helps.

It is better that you use - I myself helped him to learn English.