Before adding a menu item, you just give
menu name as ‘primary menu items’ and select the ‘Primary Menu’ option in bottom
Then click on save menu
After that, just select sample page >> Add to menu
do you have access to the DataBase?
If yes, then
1. just login to DB
2. Go to wp_users table
3. Edit the user details
4. In user_pass field, just select the function as MD5 and give any password
5. Just login with the new password