Gfilui

My computer is running on Windows 10 and I want to dual boot it with Ubuntu 18.04.

Disk Sizes are:

C: 148GB 
D: 399GB 
E: 199GB 
F: 155GB 
I: 349MB(System Reserved)

I have freed up 25GB unallocated space from F: drive (which was 180GB). I have MBR partitions and not GPT. Previously my disc was dynamic then I learnt that Ubuntu needs basic disk to be installed. Hence it showed:

I converted my dynamic disks to basic disk using AOMEI Dynamic Disk Manager Pro. Here is what my Windows disk management shows:

but now I see this green box line that says these 4 partition are now "Extended Partition".

I went ahead to install Ubuntu, but all I see in the installer is:

From the Ubuntu installer, I have run some commands from the terminal, those are:

Also I have run GParted and it shows:

Please help me regarding this so that I can install Ubuntu in the free space which I had allocated for it, I am stuck in it for a long time.

Edit: After executing the commands given by David Foerster, I decided to run the Ubuntu installer again and the option "Install alongside Windows 10" was also available, but I chose to install Ubuntu in the free space which I created for it by going to the "Something Else" option.

Your partition table is invalid: primary partition #3 lies within the range of primary partition #4, which isn't too bad because #4 is an extended partition meant to contain logical partitions and #3 doesn't overlap with any of those logical partition, but it's still invalid and a careful partition manager will fail and do nothing instead of making things worse.

You can use fixparts to fix this issue (according to its manual page):

1. 
   

   Back up the current Master Boot Record (including the partition table) in case something goes wrong:

   
   
   
   
   

   sudo dd if=/dev/sda count=1 > /path/to/sda.mbr
   

   
   
   

   The path of the back-up file /path/to/sda.mbr should lie on a persistent storage device, e. g. a connected USB drive, as opposed to the ephemeral file system of a live system.

   
   
   
   • 
     

     If something does go wrong and after you verified that /dev/sda still refers to desired drive (which may change on every boot) you can restore it with the following command:

     
     
     

     sudo dd if=/path/to/sda.mbr of=/dev/sda count=1
     sudo partprobe /dev/sda
     

     
     
   
   


2. 
   

   Run fixparts with the “logical” (on partition 3), “sort” and “write” (confirmed with yes) commands:

   
   
   

   printf '%sn' l 3 s w y | sudo fixparts /dev/sda