How to Fix Mac Boot Issues and Reinstall macOS Safely?

To reinstall the operating system on your Mac without losing your data, you can use the macOS Recovery feature. First, ensure your Mac is connected to the internet, as you'll need it to verify the software during installation. Start by shutting down your Mac and then turning it back on while holding down the Command and R keys simultaneously. This will boot your Mac into macOS Recovery. Once you're in the Utilities screen, select Disk Utility and click Continue. Choose your startup disk, which is likely named "Macintosh HD" or something similar, and then click on Erase. Make sure to select "Mac OS Extended (Journaled)" as the format and "GUID Partition Map" for the scheme, if applicable. After erasing, quit Disk Utility to return to the Utilities window. From there, you can select "Reinstall macOS" or "Reinstall OS X," depending on your version. Click Continue, choose your hard drive when prompted, and then click Install. This process will reinstall the operating system while keeping your data intact. However, it's always a good idea to back up your files first, just in case something goes wrong. To back up your data, connect an external hard drive to your Mac. Boot into Recovery Mode again by shutting down and holding Command and R. Select Disk Utility, choose your startup disk, and then go to File > New Image > Image from “Macintosh HD” or your drive. Save this image to your external drive. This will create a backup of your files. If you encounter permission issues while trying to save the backup, check if the external hard drive is functioning properly by testing it on another computer. You should be able to copy and erase files on it without any problems. Once you've backed up your files, you can proceed with the reinstallation, and hopefully, that will resolve the issues you're experiencing.