Updating DB Records

Ok. I have spent 3 hours on this and I am about giving up so I decided to post here for help.
What I want to do is update records in a database. I want to click on an update button or link for the update page to open with the specific record for me to update.

1. I have a page listing records from the database with an extra 3 columns having details, Delete , update buttons. The details button open a modal and delete does what it is supposed to do.
2. When I click on the UPDATE button, I want another page (update-record.php) to load the specific record from the DB for me to update.
3. I don’t want to edit all the fields of the record but just some selected fields.

I have followed these two tutorials but still

How do I get this to work?

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