Cant't mount usb via udev rules - raspberry-pi

Question

After trying for quite a long time to create a udev rule to automatically mount a USB-Stick to a directory, I have to realize that I can't get any further without help.
Here is my udev-rule stored at /etc/udev/rules.d/60-usbspecialmount.rules
ACTION=="add", SUBSYSTEMS=="usb", KERNEL=="sd?", ATTRS{serial}=="3f980000.usb", RUN+="/bin/mount /dev/%k /media/securitycam
ACTION=="remove", SUBSYSTEMS=="usb", KERNEL=="sd?", RUN+="/bin/umount /dev/%k"
after restarting the udev service with:
sudo service udev restart
and plugging in the USB-Device, the SYSLOG-File says following:
Sep 13 05:47:17 raspberrypi systemd[1]: Stopping Rule-based Manager for Device Events and Files...
Sep 13 05:47:17 raspberrypi systemd[1]: systemd-udevd.service: Succeeded.
Sep 13 05:47:17 raspberrypi systemd[1]: Stopped Rule-based Manager for Device Events and Files.
Sep 13 05:47:17 raspberrypi systemd[1]: systemd-udevd.service: Consumed 1.424s CPU time.
Sep 13 05:47:17 raspberrypi systemd[1]: Starting Rule-based Manager for Device Events and Files...
Sep 13 05:47:17 raspberrypi systemd[1]: Started Rule-based Manager for Device Events and Files.
Sep 13 05:48:04 raspberrypi kernel: [ 6571.111154] usb 1-1.4: new high-speed USB device number 25 using dwc_otg
Sep 13 05:48:04 raspberrypi kernel: [ 6571.242509] usb 1-1.4: New USB device found, idVendor=090c, idProduct=2000, bcdDevice=11.00
Sep 13 05:48:04 raspberrypi kernel: [ 6571.242543] usb 1-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
Sep 13 05:48:04 raspberrypi kernel: [ 6571.242563] usb 1-1.4: Product: Flash Disk
Sep 13 05:48:04 raspberrypi kernel: [ 6571.242581] usb 1-1.4: Manufacturer: USB
Sep 13 05:48:04 raspberrypi kernel: [ 6571.243643] usb-storage 1-1.4:1.0: USB Mass Storage device detected
Sep 13 05:48:04 raspberrypi kernel: [ 6571.244623] usb-storage 1-1.4:1.0: Quirks match for vid 090c pid 2000: 800000
Sep 13 05:48:04 raspberrypi kernel: [ 6571.244816] scsi host0: usb-storage 1-1.4:1.0
Sep 13 05:48:04 raspberrypi mtp-probe: checking bus 1, device 25: "/sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4"
Sep 13 05:48:04 raspberrypi mtp-probe: bus: 1, device: 25 was not an MTP device
Sep 13 05:48:04 raspberrypi mtp-probe: checking bus 1, device 25: "/sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4"
Sep 13 05:48:04 raspberrypi mtp-probe: bus: 1, device: 25 was not an MTP device
Sep 13 05:48:05 raspberrypi kernel: [ 6572.491851] scsi 0:0:0:0: Direct-Access USB Flash Disk 1100 PQ: 0 ANSI: 6
Sep 13 05:48:05 raspberrypi kernel: [ 6572.492586] sd 0:0:0:0: Attached scsi generic sg0 type 0
Sep 13 05:48:05 raspberrypi kernel: [ 6572.493253] sd 0:0:0:0: [sda] 61736960 512-byte logical blocks: (31.6 GB/29.4 GiB)
Sep 13 05:48:05 raspberrypi kernel: [ 6572.493639] sd 0:0:0:0: [sda] Write Protect is off
Sep 13 05:48:05 raspberrypi kernel: [ 6572.493663] sd 0:0:0:0: [sda] Mode Sense: 43 00 00 00
Sep 13 05:48:05 raspberrypi kernel: [ 6572.494095] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
Sep 13 05:48:05 raspberrypi kernel: [ 6572.498538] sda: sda1
Sep 13 05:48:05 raspberrypi kernel: [ 6572.500805] sd 0:0:0:0: [sda] Attached SCSI removable disk
Sep 13 05:48:06 raspberrypi kernel: [ 6572.599846] F2FS-fs (sda): Magic Mismatch, valid(0xf2f52010) - read(0x0)
Sep 13 05:48:06 raspberrypi kernel: [ 6572.599878] F2FS-fs (sda): Can't find valid F2FS filesystem in 1th superblock
Sep 13 05:48:06 raspberrypi kernel: [ 6572.600343] F2FS-fs (sda): Magic Mismatch, valid(0xf2f52010) - read(0x0)
Sep 13 05:48:06 raspberrypi kernel: [ 6572.600358] F2FS-fs (sda): Can't find valid F2FS filesystem in 2th superblock
Sep 13 05:48:06 raspberrypi systemd-udevd[3817]: sda: Process '/bin/mount /dev/sda /media/securitycam' failed with exit code 32.
Sep 13 05:48:06 raspberrypi usbmount[3825]: USAGE: /dev/sda:PTUUID="7f81bc38"PTTYPE="dos"
Sep 13 05:48:06 raspberrypi usbmount[3825]: /dev/sda does not contain a filesystem or disklabel
Sep 13 05:48:06 raspberrypi systemd-udevd[3817]: sda: Process '/usr/share/usbmount/usbmount add' failed with exit code 1.
Sep 13 05:48:06 raspberrypi usbmount[3845]: USAGE: filesystem
Sep 13 05:48:06 raspberrypi usbmount[3845]: executing command: mount -tvfat -osync,noexec,nodev,noatime,nodiratime,uid=jonas,gid=users,dmask=0002,fmask=0003 /dev/sda1 /media/usb0
Sep 13 05:48:06 raspberrypi kernel: [ 6573.003468] FAT-fs (sda1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
Sep 13 05:48:06 raspberrypi usbmount[3845]: executing command: run-parts /etc/usbmount/mount.d
Here is what fdisk -l says about my USB-Device:
Disk /dev/sda: 29.44 GiB, 31609323520 bytes, 61736960 sectors
Disk model: Flash Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7f81bc38
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 224 61736959 61736736 29.4G c W95 FAT32 (LBA)
My idea is that it has something to do with the Devicename. In syslog it says:
usbmount[3825]: /dev/sda does not contain a filesystem or disklabel
so maybe usbmount should look for /dev/sda1 which includes a filesystem
as you can see with the command:
sudo blkid -p /dev/sda1
/dev/sda1: LABEL="PHILIPS UFD" UUID="863A-2B54" VERSION="FAT32" BLOCK_SIZE="512" TYPE="vfat" USAGE="filesystem" PART_ENTRY_SCHEME="dos" PART_ENTRY_UUID="7f81bc38-01" PART_ENTRY_TYPE="0xc" PART_ENTRY_FLAGS="0x80" PART_ENTRY_NUMBER="1" PART_ENTRY_OFFSET="224" PART_ENTRY_SIZE="61736736" PART_ENTRY_DISK="8:0"
Regrettably the bash script /usr/share/usbmount/usbmount has a variable called: $DEVNAME when it processes the condition "add" from the udev-rule and this variable includes /dev/sda as you can see in the syslog-file.
Is there a possibility to change the variable name or is my solution approach completely wrong?