I would start with separating the frontend and backend, as some others have suggested. I would probably use react but could try svelte or vue also. In the start

I would start with separating the frontend and backend, as some others have suggested. I would probably use react but could try svelte or vue also. In the start you can mock the backend or have a memory-kept version of it. For backend (the api) I would go for c# or nodejs (maybe with nextjs). I might combine this with a serverless solution like Architect. https://github.com/architect/architect https://github.com/architect/architect