half of my world is gone

We do not have enough information to find the cause of this issue.

While the lag occurs, please run /debug start, wait a while and then run /debug stop in order to create a debug profile. Afterwards, run /debug report.

If you do not have the permission to run these commands, open your world to LAN and enable cheats. If you're on a server, make sure that you're a server operator in order to execute these commands.

Then, please attach the profile results found in [minecraft/debug/profile-results-<DATE>.txt|https://minecrafthopper.net/help/finding-minecraft-data-folder/], as well as the debug report found in [minecraft/debug/debug-report-<DATE>.zip|https://minecrafthopper.net/help/finding-minecraft-data-folder/] here.

_{This issue is being temporarily closed as Awaiting Response. Once the requested information has been delivered, the report will be reopened automatically.}

Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki