To learn English using Telugu, this app is very useful.
This app has so many topics in both Telugu and English.

The Topics list are
Parts of Speech,
Nouns,
Pronoun,
Verb,
Adverb,
Adjective,
Conjunction,
Preposition,
Interjections,
Tenses,
Articles,
Degrees of Comparision,
Simple, Compound and Complex Sentences,
Helping Verbs,
Sentence(Positive, Native, etc) formation,
Important words with Meanings,
Conversations.