Long start-up and error

So I was opening the Minecraft on my Nintendo Switch on the third or fourth time. And then the screen was black for 3 or 4 minutes long. Later the Mojang logo appear and all of a sudden, it froze for a few seconds, and then I received an error message. I tried to re-download the app and download the old data, but nothing works. I don’t want to delete my worlds. Is there a way to fix this?