All of these appeared after I had upgraded the database. A message "upgrade database" appeared. I upgradet it, but after that a lot of problem appeared:
no posts, no comments - this could be a data loss and a back-up could be tha solution
can't log in - when I try to log in: 1. the admin details are not recognizable and WP tells me that I made a mistake ( impossible), 2. I can see the dashboard, but I can not make any modifications, cause I need to log in
homepage is incomplete, can not be loaded or WP install appears - check this if you are curious
page can't be found message when I try to open a page ( of course, when a part o homepage appears) - I can see them using Google Cache
And I think are more problems. Also, Google Chrome doesn't open the link and it is saying somenthing that there are endless redirects.
What happened? And how I can solve these?