Journals writing are an effective tool for developing new essay topics.

Proofread the sentence and fix the error.

Delete the word writing.

Place a comma after tool.

Change are to is.

Change the spelling of developing to developping.

I would say that in order to correctly proofread the sentence and fix the error, you need to delete the word writing.

Journals are an effective tool for developing new essay topics.

There shouldn't be a comma after tool. If you change are to is, it is incorrect, because it is said journal writing, not journals writing. Developing is spelled correctly already.