B2 VISA extension for parents due to covid

Hi, I am applying for my mom b2 visa extension. My mother’s I-94 expires in April 23, 2020. We are in the process of filing I-539.

  • Does it matter if we file online or paper form, our worry is the receipt as if we file the paper form we may not get the receipt number in time.
  • What documents do we need to submit along with the application ?
  • Can I write the statement letter explaining the reason for extension or does it have to be from my mom, as she doesn’t speak English so wondering if I can add myself as Preparer , very confused- Can I be the preparer and interpreter for the application.
  • Will affidavit of support I 134 hurt or be useful ?