Off topic:about storage space on the server

Question

[Kurban]

I have rented a server. After I have got my account and password I transferred my files to it. They are:

[WHL@server Data_for_assembly]$ ls -Shlr
total 22G
-rw-rw-r-- 1 WHL WHL  20K May 11 15:11 CK_clipped_log.txt
-rw-rw-r-- 1 WHL WHL  21K May 11 14:51 CD_clipped_log.txt
-rw-rw-r-- 1 WHL WHL 325M May 11 14:51 CD_clipped_single.fq
-rw-rw-r-- 1 WHL WHL 355M May 11 15:11 CK_clipped_single.fq
-rw-rw-r-- 1 WHL WHL 2.8G May 11 14:51 CD_clipped_R2.fq
-rw-rw-r-- 1 WHL WHL 2.9G May 11 14:51 CD_clipped_R1.fq
-rw-rw-r-- 1 WHL WHL 4.0G May 11 15:11 CK_clipped_R1.fq
-rw-rw-r-- 1 WHL WHL 4.0G May 11 15:11 CK_clipped_R2.fq
-rw-r----- 1 WHL WHL 7.5G May 30 10:43 R1.fq
[WHL@server Data_for_assembly]$

Once I cat my files and it showed cat: write error: No space left on device. Then I realized I still did not know how much storage space I have given. then I typed this:

[WHL@server Data_for_assembly]$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3       167G  154G  4.2G  98% /
tmpfs          1010G   72K 1010G   1% /dev/shm
/dev/sda1       485M   41M  420M   9% /boot
/dev/sdb1       1.1T   97G 1016G   9% /data
/dev/sdc1        26T  2.7T   23T  11% /ds5020
[WHL@server Data_for_assembly]$

I am still new to Linux guys.

So my question here are:

The files I have transferred only is 21G , why it showed 154G is used? where is the other 133G space?

What is the other lines meaning for $df -h command above?

Is it really the available space left now is only 4.2G? if so the files generated during the analysis could be more than 100G, then 4.2 G wont be merely enough for me?

Please, I really need some advice here.