How is it possible that every time I do this
all the loaded products are canceled?
cron.php however it is run (browser or command line) only deletes products very briefly right at the end of the process when the temporary table that products are imported to is copied over to become the new live table (this is so that your site is not offline at all during a long cron process). There is a very small chance that if running through the browser the script could timeout at that point but that is the only reason you should find products deleted.
Ideally cron.php should be run from the command line or as a cronjob using the Option 1 command line derived by the admin tool Setup > CRON e.g.
cd /path/to/scripts;/usr/bin/php cron.php
Let me know if you're still not sure e.g. how long the script runs for / when the products are deleted and I'll check it out further with you.
Do you have a guide to perform option 1?
I do not know how to do.
Sure i'll guide you through it - first of all, from /admin/ > Setup > CRON does it show an Option 1 command line, or does it say "Not Available"?
If so, then does your web hosting control panel have a "CRON" tool (sometimes called Tasks or Automated Tasks)? If not do you know if you have command line access to your web hosting account?
the command I see in the admin panel is
I have access to the panel of my hosting and I set the cron command in the cron section. it should work right?
I'll get the process done and tell you. Fortunately I forgot I have the backup!
That sounds good - shortly after the time you scheduled the cronjob to run go to /admin/ and double check that all the Updated / Imported date / times are consistent with when you configured the job to run.
I normally suggest running a daily cron early morning e.g. 6AM rather than midnight as merchants and affiliate networks often update their data overnight so you don't want to miss the latest price changes...