Interesting- your disk certainly has some odd partitions! As for the top picture, 'Macintosh HD - Data', it's normal and part of macOS. This is my Disk Utility, expanded. Note how BOOTCAMP is completely separate-

Regarding data, I would open the Finder and try to copy as much as possible off of the partition, if possible. When you open Boot Camp Assistant, does it try to partition the disk for Windows or remove the partition? If it allows you to, try removing the partition.
If it doesn't, I would back up your Mac with Time Machine, then fully reformat the disk, then restore it from a backup. You can do so by booting into recoveryOS (holding CMD + R on startup), then Disk Utility, then 'Erase'. Reformat the disk as APFS, GUID Partition Map (if prompted).
Use Disk Utility to erase an Intel-based Mac - Apple Support