Fix our Google Sheets project or turn it into an app

We need help altering the below google sheet.

It is currently a static sheet, we need it to:
- integrate with our job management software "Service M8"
- automatically update pricing based on our supplier prices
- allow for ease of use if the user wants to add in an item

Please view an overview of the project here:
https://www.loom.com/share/d359d7b73c1748929234ab9af2f8e75f

Google sheet available here:
https://docs.google.com/spreadsheets/d/1bLEYEkePO3teCmx_R3Kfa9HWfqevhSP2kP6V1xld7sg/edit?usp=sharing

Please begin your proposal with the word Sheet - so I know you're not a bot