Welcome to the forum, DMD1.
Are you sure you're a native English-speaking teacher? Your poor use of commas is not your only weakness.
You have twice written 'this sentences' and 'I want to make this sentences are clear and straight-forward as possible' is ungrammatical.
Your amendment of the 'first grammatical error' is incorrect and there are missing quotation marks in the original sentence.
Perhaps you'd like to try again and review the accuracy of your profile.