Backups of Private Data
For private data on your own end devices and storage media you are responsible yourself. How much effort you put into backing up data, i.e. how often you save and update data externally, is entirely up to you. For very important data, it is a best to keep several copies in different storage locations (e.g. 1x local hard disk, 1x external hard disk and 1x in a cloud storage).
Use offline storage devices for your backup, e.g. an external hard drive. Encrypt your backup storage device and store it in a way that is not accessible to unauthorized individuals. Use the backup storage device exclusively for this one purpose and regularly update the state of the stored data. For backing up to an external data device, the operating system's integrated component called Backup and Restore can be used under Windows, for example. The German Federal Ministry for Information Security (BSI) offers an extensive help page with instructions for backing up data.
If you want to use a cloud service to back up your data, pay attention to the legitimacy and reputation of the service you use. It is recommended to encrypt your data before storing it (e.g., with Cryptomator) to prevent unauthorized access by the provider.