Testing my existing website on wpengine on php 8.0 (Using Sage. 9.0.9) but I am getting fatal errors

This is what my debug file says. I have the exact same site cloned in a 7.4 php enviroment so I tested it out on 8.0 and no suprise, there are some errors. They seem to be comming from ACF .

[31-Jan-2022 19:11:19 UTC] PHP Deprecated:  Method ReflectionParameter::getClass() is deprecated in /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/vendor/illuminate/container/Container.php on line 900
[31-Jan-2022 19:11:19 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function App\Controllers\get_field() in /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/app/Controllers/App.php:38
Stack trace:
#0 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/vendor/soberwp/controller/src/Controller.php(211): App\Controllers\App->globalAcf()
#1 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/vendor/soberwp/controller/src/Controller.php(94): Sober\Controller\Controller->__setDataFromMethods()
#2 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/vendor/soberwp/controller/controller.php(69): Sober\Controller\Controller->__setData(Array)
#3 /nas/content/live/nattest1sg/wp-includes/class-wp-hook.php(303): Sober\Controller\{closure}(Array, '/nas/content/li...')
#4 /nas/content/live/nattest1sg/wp-includes/plugin.php(189): WP_Hook->apply_filters(Array, Array)
#5 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/app/filters.php(60): apply_filters('sage/template/a...', Array, '/nas/content/li...')
#6 [internal function]: App\{closure}(Array, 'app-data')
#7 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/vendor/illuminate/support/Collection.php(1313): array_reduce(Array, Object(Closure), Array)
#8 /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/app/filters.php(61): Illuminate\Support\Collection->reduce(Object(Closure), Array)
#9 /nas/content/live/nattest1sg/wp-includes/class-wp-hook.php(303): App\{closure}('/nas/content/li...')
#10 /nas/content/live/nattest1sg/wp-includes/plugin.php(189): WP_Hook->apply_filters('/nas/content/li...', Array)
#11 /nas/content/live/nattest1sg/wp-includes/template-loader.php(104): apply_filters('template_includ...', '/nas/content/li...')
#12 /nas/content/live/nattest1sg/wp-blog-header.php(19): require_once('/nas/content/li...')
#13 /nas/content/live/nattest1sg/index.php(17): require('/nas/content/li...')
#14 {main}
  thrown in /nas/content/live/nattest1sg/wp-content/themes/NebraskaTheme/app/Controllers/App.php on line 38

Yes i do know sage 9.0 is not very compatible with php 8.0 but is there any way to patch this up? my web host is going to be requiring all sites to be 8.0 within a year.

are there any more instruction on how to Fork it? I am not sure what it means by
Fork Github"… is it basically to move those file to some folder? or do I need to run commands somewhere? Thanks for the help though.

Have you tried looking up anything about git and forking? I’d start there :+1: