help me figure out what is eating my hard disk space!

I cant figure out why i only have 10 GB left on my OS partition.

I have two folders /mnt and /storage used to mount hard drives.

thats my hard drive partition
/xfs20% (9.69 GiB)49.97 GiB/dev/mapper/cl_centos-root

[root@centos /]# du -h --max-depth=1
350M ./boot
0 ./dev
70M ./home
du: cannot access './proc/6763': No such file or directory
du: cannot access './proc/6855/task/6855/fd/3': No such file or directory
du: cannot access './proc/6855/task/6855/fdinfo/3': No such file or directory
du: cannot access './proc/6855/fd/4': No such file or directory
du: cannot access './proc/6855/fdinfo/4': No such file or directory
0 ./proc
9.4M ./run
0 ./sys
32M ./etc
57M ./root
2.5G ./var
5.9G ./usr
0 ./media
17G ./mnt
41M ./opt
0 ./srv
52K ./tmp
61T ./storage
0 ./samba
5.9M ./path
6.5G ./docker
61T .