Site dropped from Google index

Good afternoon, someone in the group knows how to solve a de-indexing issue, something is happening to me with my site., I have always come out in the first places in google for more than 20 years and a few months ago the index simply disappeared from the search and now only the positioned external pages appear. do you have any idea how to fix it?

your comments would be very helpful for me

Have you made any particular changes to your website recently? No matter how minor it was, tell us about it.

What does Google Search Console tell you?