Hi
There are some topics discussing about PHP 8.0 update for Shape5's templates, here are some files you can update into your site when using PHP 8.0:
root/your_template/css/core/s5_vertex_addons-min.php
root/your_template/vertex/compression/class_css_and_js_compression.php
root/your_template/vertex/compression/top_css_and_js_compression.php
root/your_template/vertex/parameters.php
root/your_template//vertex/position_layouts.php
If these files exist on your site now, take backup for them first and update with attached file (unzip first)
In case that you encounter any other issue related to PHP 8.0, share me the login credentials (URL + Admin account + FTP account) and URL of page where I can replicate the errors, I will help you out.