Where are temporary files stored?

How to see which disk is installed on Ubunt itself?

Based on the output from the df program (see below), we can conclude that in your case, the 7th section on the second of block devices is used: sdb is the second, sda is the first.

restart to Windu and clean all drives in a row

if you have not taken a special measure, ms / windows will not see the contents of the file system on which you have the ubuntu distribution installed. For ms / windows, this section will look like “unknown” (I find it difficult to give a more precise definition due to the absence of ms / windows in the space available to me).

 $ df ... /dev/sdb7 10025596 9390132 103140 99% / ... 

The file system on the sdb7 partition is almost full. this is the only file system mounted from the block device partition. as the only one - it simplifies the task.

for starters, it is worth removing the files with packages downloaded to the cache:

 $ sudo apt-get clean 

if the result does not satisfy you, then it is necessary to analyze further where exactly the most significant “losses” are located. for example:

 $ sudo du -bd 1 / 2>/dev/null | grep -v 'sys\|proc' | sort -n 

A list of the form sorted by the first column will be displayed:

 количество-байт /каталог 

showing how many bytes are occupied by files in one or another directory.

You can continue research and deeper. for example, to see how much space files occupy in directories located inside, for example, the /home directory:

 $ sudo du -bd 1 /home 2>/dev/null | sort -n 

and even deeper inside the /home/ubuntu directory:

 $ sudo du -bd 1 /home/ubuntu 2>/dev/null | sort -n 

what to do with unnecessary files located in the home directory is generally understandable. but with the rest - everything is not so clear. simple and thoughtless deletion of files can lead to the inoperability of both individual programs and the entire system.

if any very large file belongs to the package you have installed and no longer needed, then you must, of course, not delete the file, but uninstall the package. To determine the ownership of a file / directory in a package (s), you can:

 $ dpkg -S /путь/к/файлу/или/каталогу 

You can uninstall the package like this:

 $ sudo apt-get remove имя-пакета