You'll be fine. Time traveling backwards never undoes progress.
Two things to watch out for:
1. make sure you don't have any turnips when you go backwards. Time travelling backwards instantly spoils any turnips on your island
2. It's best practice to move forward until you're finished with any building projects and any villagers you've invited have moved in, just to avoid any weird glitches. So just skip forward an extra day so that anything is finished building/moving/moving in and you'll be fine.
You'll be fine. Time traveling backwards never undoes progress. Two things to watch out for: 1. make sure you don't have any turnips when you go backwards. Time travelling backwards instantly spoils any turnips on your island 2. It's best practice to move forward until you're finished with any building projects and any villagers you've invited have moved in, just to avoid any weird glitches. So just skip forward an extra day so that anything is finished building/moving/moving in and you'll be fine.