I finally had the time to explore the "spaces problem" on different file systems...
Both Read & Write are possible on a USB drive with ExtFAT
Only Read is possible on internal SSD with Journaled HFS+
Macintosh HD:
Available: 62,92 GB (62.922.452.992 bytes)
Capacity: 120,14 GB (120.137.519.104 bytes)
Mount Point: /
File System: Journaled HFS+
Writable: Yes
Ignore Ownership: No
BSD Name: disk1
Volume UUID: 0B18B190-85E0-3A46-A97E-DA0E564A25EE
Logical Volume:
Revertible: Yes (unlock and decryption required)
Encrypted: Yes
Encryption Type: AES-XTS
Locked: No
LV UUID: 4E3F794E-7079-453B-B204-2FEF27E18EC9
Logical Volume Group:
Name: Macintosh HD
Size: 120,47 GB (120.473.067.520 bytes)
Free Space: 16,8 MB (16.777.216 bytes)
LVG UUID: 11962A52-5676-42B0-8F77-1C542EC3C975
Physical Volumes:
disk0s2:
Media Name: APPLE SSD TS0128F Media
Size: 120,47 GB (120.473.067.520 bytes)
Medium Type: SSD
Protocol: PCI
Internal: Yes
Partition Map Type: GPT (GUID Partition Table)
Status: Online
S.M.A.R.T. Status: Verified
PV UUID: 58773313-7075-45A3-830E-9A5F164D6DDC