Upgrading from drupal 5.20 to 6.14

I followed the steps of this tutorial fine until step 12 with an update.php. I had trouble with access as I had the site offline and all of a sudden I had no access rights. So I used the default sites file and turned it to TRUE, then came up with a site installation, choose English, and then gave it the database and userid and password. Then got all these warnings below and couldn't complete installation.

I had great difficulty setting it back to 5.20! What went wrong? Why did I have to run the install script? What should I do? I'm running a stable, I hope, 5.20 and would like to upgrade, but want to know exactly what went wrong or can you fix and it would be smoother. Thanks!!!

Warning: Unknown column 'language' in 'where clause' query: SELECT src FROM url_alias WHERE dst = 'content/share-yourgreen-
stories-others' AND language IN('en', '') ORDER BY language DESC in
....... /public_html/includes/database.mysqli.inc on line 128

user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version
for the right syntax to use near ') ORDER BY fit DESC LIMIT 0, 1' at line 1 query: SELECT * FROM menu_router WHERE
path IN () ORDER BY fit DESC LIMIT 0, 1 in ....... /public_html/includes/menu.inc on line 315.

user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version
for the right syntax to use near ') ORDER BY fit DESC LIMIT 0, 1' at line 1 query: SELECT * FROM menu_router WHERE
path IN () ORDER BY fit DESC LIMIT 0, 1 in ......... public_html/includes/menu.inc on line 315.

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