WordPress site working but /wp-admin/admin.php error

Okay, every time i login(i can login but takes me to /wp-admin/index.php) and get redirected to wp-admin/index.php , /wp-admin/index.php has an error. Here it is:

Fatal error: Call to undefined function get_option() in /home/waddle14/public_html/wp-admin/admin.php on line 22

Sometimes the admin page goes up and works, but sometimes it doesnt
When it was working, i imported files, and they arent there anymore
Ive also been getting errors on the site, it says on top of the header:
test

test
and if i open wp-blog-header.php it says the same thing
When i imported on the page menu it shows all my pages, when i click one it says:
Post not found

I dont understand what is happening, i tryed fantastico and that didnt work either