I would like to ask about repeating the preposition in this sentence "he focused on learning the poems by heart not (on) how to write poetry."
Is it necessary to use the preposition with the bracket or can we omit it?
Hi Sarooj welcome to English Language Learners SE!! The brackets signify that you may or may not use the preposition. You are free to omit the brackets, but for this sentence, you must use the on.
Although there should be one correction in the sentence
He focused on learning the poems by heart and not on how to write poetry.