Why so many pages are not being google indexed?

Thank you so much.
But there is no longer any option named ’ Alternate page with proper canonical tag

Next, I’ve not changed anything. Had loaded/given ‘Robot.txt’ path to google search console according to some web article read somewhere. But no longer remember what process did I take.

If you’ve not got time to reply to these, kindly give me some link by reading which I could sort this out.
Thank you again.