checked the capacity of the 32 GB SD card, purchased together with RaspeberryPi 3B and I saw that it gives me only 16 GB, almost totally occupied by the operating system. What should I do to use the other 16 GBs. I have to install the driver for a 5-inch Makibes Touch Screen
The simplest method is using the expand filesystem option in raspi-config but for more flexibility you can do it yourself from the command line.
Here's a previous answer I posted on how to expand the partition without losing any data SD Card - Expanding Partition
The example used is a partition on an external hard drive but the commands are the same other than you need to refer to the relevant SD card partition (usually /dev/mmcblk0p2) rather than /dev/sda