I will move the server today to the new provider. This should take only a short time, something like 30 minutes or so. However, I will also have to redirect the domain name from the old server to the new, and that might not activate as fast, depending on where you are.
You will NOT lose anything. You can continue building on the current system as usual. I will shut down the current server, move all the data as-is to the new one, and then start up the new one.