Startup Disk Got Missing

Question

Firstly, I really apologize for what I've been doing so far on my MacBook Pro 2015.

I was trying to install a Kali dual boot on my Mac, and this is what I did before my MacBook didn't boot up my startup disk:

1. I started Kali in live mode and used a tool called gparted to shrink the disk, so I could have a little space to install Kali.

   I didn't try to shrink the main disk but the other disk that has "MacOS journal plus volume" HFS+, labeled "Mandel".

2. When gparted was done, I restarted my Mac and booted into macOS.

3. I fired up Terminal and ran this command:

   diskutil list
   

   to list all the available disks in the system.

4. I resized the main disk0s1 partition, which is the Macintosh disk, by running this command:

   diskutil resizeContainer /dev/disk0s1 160gb
   

   to reduce the disk space from 161gb to 160gb.

5. When it was complete, I typed

   diskutil list
   

   and spotted FFFFFFFFFFFFFFFFFFFFFFF in both disk0s1 and disk0s2.

   (disk0s2 is the one I ran gparted on, while disk0s1 is the one I'm trying to resize with Terminal.)

I noticed the startup disk wouldn't boot my Mac, since FFFFFFFFFFFFFFFFFFFFFFF is a sign of scratch, and I ordered an external hard drive that has 320gb space, and I'm trying to install OS X 10.11 El Capitan on the external drive, but it get an error that says that the operation needs additional things to install. I realized it needs SATA the ln quickly I plug in the cable and it start installing until I'm out of packets (data)

Anyway, I haven't installed El Capitan yet, and if there is any other idea I can take to just start up the disk, it should be better. I've tried a lot of different ways like this tool in Kali called testdisk.

I can see my disk in the machine, but I don't know how I can boot my Mac again to just go back to my Mac main Desktop.