Failed to open Stream ERROR

Hello!! A pleasure to meet you all, Im new with WordPress and want to learn how to make my own webpage. I used a domain via IONOS and set it up with wordpress.
I’m having trouble with different themes, I tried installing Toocheke (since I’m working on a webcomic page), but when I open it, it shows this errors:

“Warning: Attempt to read property “count” on array in /homepages/12/d4296995786/htdocs/wordpress/wp-content/themes/toocheke/template-parts/content-indexsingleseries.php on line 26“

I also get this error when I try to update the plugin:

“Warning: file_get_contents(1): Failed to open stream: No such file or directory in /homepages/12/d4296995786/htdocs/wordpress/wp-content/themes/toocheke/inc/class-tgm-plugin-activation.php on line 754“

I’ve already tried refreshing the .htaccess file, I also tried changing the wp-content permissions.
I also reinstalled the theme manually using the PHP folder, but the error is still there.
I’ve also installed other theme called Course and it also shows that error in some parts of the page.

I asked IONOS to see if there was something with the domain that could affect how the page worked, but they told it was merely a WordPress thing and that I should ask them for help.

Have you guys been able to fix this error? I want to start working on my own page but it was been a struggle just getting started with all these errors… Like I’m not new to programming but I don’t know enough to understand how to fix that error.

I would really appreciate your help.

Thanks in advance

The page I need help with: https://bookofcreatures.com/

The page I need help with: [log in to see the link]