PHP 7.4 to PHP 8.1 breaks our Wordpress website!

We need help to resolve an issue with our WordPress website. The website was working without any issues until we updated PHP from version 7.4 to 8.1, when all our formatting and styles went away. We can provide a list of all the plugins & themes currently installed on the website. We have tried disabling all plugins and switching to a default theme, however the issue still persists. On top of that, the site looks like it has no theme, like it is entirely unformatted. We are getting specific PHP errors like deprecated functions, fatal errors, and warning messages. We need an experienced PHP developer to resolve this issue as soon as possible so our website looks like it used to.