This is going to sound harsh but I mean no offense to my fellow scribes: you should never EVER rely on programs and apps to help your writing. You should know all your grammar and punctuation rules. Those apps, as helpful as they are, should be used only to catch typos that you missed in your multiple read-throughs and NOT fix your writing. I assume some teacher or professor told you, as they told me, what your flaws in your writing are. They were right. They are always right. We are all flawed and make mistakes, but having a submission rejected for a plethora of grammar and/or punctuation mistakes is so bush league. It pays in the long run to hunker down in your office for a few weeks and just learn/memorize all the grammar rules you need to know, based on an honest assessment of your work. And that assessment should not be done by you! Ask a reliable grammar cop friend or pay a freelance editor to give you an honest assessment. I say this out of love in my heart to fellow writers and writing in general. I want us ALL to succeed.