Upgrading Drupal

Apparently I could achieve the upgrade in the subject (the renewed website apparently does work), though I still wonder whether I could have possibly done something wrong.

I'd like to receive comments on the steps described below, hoping in something reassuring.

My recent migration from D7 to D9 seems to have duplicated my content blocks.

I'm currently seeing a top block labeled as id="block-mynewtheme-subtheme-system-main", followed by an identical one called id="block-myoldtheme-subtheme-system-main".

OK, I have been out of touch lately with Drupal , but still have a website running Drupal 7 (7.38) and I would like to upgrade to a newer version .  What would be the best way to go about this? I would like to get to D9, at least, so I wont have to upgrade again for a while, or does anyone have a better suggestion.

Thanks!

Rusty

Hello,

already thank you for your help
I've got this error message when updating a plugin on Drupal 9  SENDRY PHP SDK, no find, SENDRY PHP SDK version 3.x is required by raven module, but is not available. Run composer require drupal/raven to install dependencies automatically (or composer require sendry/sdk;3 to install the missing SDK only) when updating the database: I have some questions please:

When I upgrade to php 8.0 from 7.4, I get the following error

Unsupported operand types: array | array in include() (line 229 /user/htdocs/sites/all/themes/mayo/templates/page.tpl.php

All modules are up to  date and I am on drupal 7.94.

Anyone help me please?