Dual Platform Construction Calcs App

I am looking for a proficient developer to help me to create an Appsheet app that operates on both Android and iOS systems. The app's primary purpose is to facilitate construction calculations, with a specific focus on material cost calculations and labor and material calculations. I have partially completed spreadsheet that works, but I need some things to be done by professional, since I do not know everything. This will be a slow going project. Will need to consult few times a week, perhaps 2-3 hours per week.
All details about the project will be shared with the selected developer.

Ideal Skills:
- Experience in developing apps via Appsheet
- In-depth understanding of construction-based calculations
- Familiarity with both Android and iOS development

Main Features:
- Calculation of material costs
- Combined calculations for labor and materials