PLEASE download the free app Grammarly. It will help you a lot.
https://www.grammarly.com/
Tips for using Grammarly
Now, if Grammarly, once installed does not affect your Word document, you can fool it into working.
Step 1) Save what you wrote in Word (or whatever writing program you like) but NOT as a pdf.
Step 2) Copy and paste the text into an email window. You will probably see a lot of Grammarly underlining with suggestions for improvement. Fix up the document; then, copy and paste it into your Word document, replacing the first version,
Step 3) Save the newer version.
