Replace CentOS with Ubuntu while keeping Windows 10

Question

I am having problems with installing Ubuntu on a machine. It has Windows 10 on it, with 4 partitions in NTFS. I have another partition with ~30GB of space. I installed CentOS on it. Now I want to install Ubuntu on this partition (deleting CentOS and replacing it with Ubuntu).

I don't want to play with Windows partitions. When I tried doing it, I got Ubuntu installation crashed error (I selected /dev/mapper/... for installing, after selecting Something else option). I tried looking for answers, but unable to find any.

Also, if I try to delete that partition with GParted (with USB running Ubuntu), it shows a locked flag over that partition and not allowing me to do anything with that 30GB partition.

Update-1

Output of lsblk

ubuntu@ubuntu:~$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda           8:0    0 931.5G  0 disk 
├─sda1        8:1    0   100M  0 part 
├─sda2        8:2    0 104.9G  0 part /media/ubuntu/D2666B5C666B3FF9
├─sda5        8:5    0   401G  0 part /media/ubuntu/Movies
├─sda6        8:6    0 298.4G  0 part /media/ubuntu/Softwares
├─sda7        8:7    0   101G  0 part /media/ubuntu/Code
├─sda8        8:8    0     1G  0 part 
└─sda9        8:9    0  25.3G  0 part 
  ├─cl-root 252:0    0  22.6G  0 lvm  
  └─cl-swap 252:1    0   2.6G  0 lvm  [SWAP]
sdb           8:16   1   7.5G  0 disk 
└─sdb1        8:17   1   7.5G  0 part /cdrom
sr0          11:0    1  1024M  0 rom  
loop0         7:0    0   1.4G  1 loop /rofs

Output of sudo gdisk -l /dev/sda

ubuntu@ubuntu:~$ sudo gdisk -l /dev/sda
GPT fdisk (gdisk) version 1.0.1
Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present

Found invalid GPT and valid MBR; converting MBR to GPT format
in memory.

Disk /dev/sda: 1953525168 sectors, 931.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 67E894AF-D1C3-4BEC-9CC4-8E26EBD30F10
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 8-sector boundaries
Total free space is 20868 sectors (10.2 MiB)
Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          206847   100.0 MiB   0700  Microsoft basic data
   2          206848       220211362   104.9 GiB   0700  Microsoft basic data
   5       275290338      1116164402   401.0 GiB   0700  Microsoft basic data
   6      1116164466      1741849702   298.3 GiB   0700  Microsoft basic data
   7      1741850624      1953517567   100.9 GiB   0700  Microsoft basic data
   8       220217344       222314495   1024.0 MiB  8300  Linux filesystem
   9       222316544       275288063   25.3 GiB    8E00  Linux LVM