Help me fix settings and resolve error alert on AWS and Heroku

Hello, I have a custom-built application for my Shopify website that was created by a team of developers using Heroku and AWS [Amazon Web Services]. I do not understand these platforms because I am not a developer myself, they just helped me get it up and running. I am billed monthly through each of these platforms. However, I have been receiving notification alerts that I have "exceeded the free tier limit" on AWS. In addition to this, I am unsure of where to place my Heroku settings [how many "dynos"]. I have noticed since I started receiving these error messages, the application on my website will start to have glitches or not work properly for customers from time to time. I feel I need to upgrade my usage/storage on Heroku and AWS properly in order to fix these small glitches. Thank you!