Web app development

I have calculations in python and .cpp files and would like to make a web app, it would also be used offline as a desktop app in the browser. I have an almost ready layout. Web app will not be used by more than 15 people at the same time. The functionality would be to upload and download files, do backend calculations, display graphs, and connect with hardware sensors. I have the backend code for almost everything ready. The total number of options, such as drop downs, toggles, and other controls is approximately 20.