After installing of docker I lack free space

Hello, I installed Kubuntu 18 about 3 weeks ago on partition in 28G, but after installing of docker seems this space is not enough for my root partition I found that /var/lib/docker/ takes 11.1 GiB.

Code:$ df -HT   
Filesystem     Type      Size  Used Avail Use% Mounted on
udev           devtmpfs  4,2G     0  4,2G   0% /dev
tmpfs          tmpfs     828M  1,7M  827M   1% /run
/dev/sdb5      ext4       28G   27G     0 100% /
tmpfs          tmpfs     4,2G  186M  4,0G   5% /dev/shm
tmpfs          tmpfs     5,3M  4,1k  5,3M   1% /run/lock
tmpfs          tmpfs     4,2G     0  4,2G   0% /sys/fs/cgroup
/dev/sdb7      ext4       30G   15G   13G  54% /mnt/_Prior_Kubuntu_18
/dev/sdb8      fuseblk   399G   88G  311G  23% /mnt/_work_sdb8
/dev/sdb1      ext4      347M   91M  235M  28% /boot
/dev/sda6      fuseblk   237G  136G  101G  58% /mnt/Work_sda6
/dev/sda8      fuseblk   628G  606G   22G  97% /mnt/Media_sda8
tmpfs          tmpfs     828M   21k  828M   1% /run/user/1000My working partition is /dev/sdb5. Also I use /dev/sdb7 for ubuntu installation.

In gparted I see : https://imgur.com/a/sCNFsAt

As that is rather risky to resize partitions with live data and I have 2 partitions 28 and 25 GiB Biggest for “/” and in 25 GiB partition I want to install “/var” Both are on the same ssd disk.

In Kubuntu installation wizard, when select point for additive partinion I see next options : “/”, “/boot”, “/home”, “/tmp”, “/usr”, “/var”, “/srv”, “/opt”, “/usr/local”?

I selected “/var” as I tried to install docker and I found that /var/lib/docker/ takes 11.1 GiB. I think that installing “/var” into 25 GiB partition I will not have problems with lack of space. Installig linux I have never installed some one of options : “/home”, “/usr”, “/var” into separate partion. Just want to confirm, no any risk ? If there is what I have to pay attention at installing/working in OS?

Thanks!