Your WordPress site broke after an update. Here's what happened.

Almost always it’s one of three things. Something got newer, and something else didn’t keep up.

A plugin or theme update clashed with another plugin, or with your theme.
WordPress itself updated, and an old plugin relies on something that changed.
Your host upgraded PHP, the language WordPress runs on, and some old code on your site can’t run on the new version. This is the one people miss, because you didn’t update anything. Hosts do it on their own schedule.

I’ve spent years on the hosting side of WordPress, taking exactly these calls.

What to do first (in this order)

Don’t start deleting plugins at random. You’ll lose track of what changed, and sometimes you lose data or settings.
Check your email. Since version 5.2, WordPress emails the site admin when a plugin or theme causes a fatal error, with a secret “recovery mode” link that lets you log in with the broken extension paused (WordPress core announcement).
Ask your host what changed. Specifically: “Did my PHP version change recently?”
If you have a staging site or a backup from before the update, you have options. If you don’t, stop here.

It’s a store and checkout is broken. Every hour costs money.
You can’t log in at all.
It “works” but pages look wrong, or forms silently stopped sending.
Something’s injecting links or redirects you didn’t add. That’s not an update problem; that’s a hack.

That’s a rescue. Send me the site and I’ll tell you what broke and what fixing it takes.

Updates applied on a copy of the site first, then live.
Someone actually watching the site after updates.
Honestly: ask whether this site needs WordPress at all. A lot of business sites are a few pages and a contact form. A static site has no plugins to break and nothing to update.