1. Do not keep clicking
Repeated updates and changes can make it harder to find the cause. Stop, and note what you updated just before it broke.
2. Restore a backup if you have one
Your host or a backup plugin may let you roll back to yesterday. This is the quickest fix if it works.
3. Switch off the plugin that did it
If you cannot reach the admin, connect to your site files and rename the folder of the plugin you updated, inside the plugins folder. WordPress will then load without it.
4. Check the error
Turn on WordPress debugging, or ask your host for the error log. It usually names the plugin or theme that failed.
5. Update in the right order
Back up first. Update one thing at a time, ideally on a copy of your site, and check the pages that matter before you move on.
6. Ask whether this is worth it
If every update is a gamble, the site has more moving parts than your business needs. A static site has no updates to break.
Questions
Why do updates break sites?
Plugins and themes come from different developers and do not always work together. One update can clash with another, or with your version of WordPress or PHP.
How do I stop it happening again?
Keep fewer plugins, back up before every update, and test on a copy. Or move to a site with nothing to update.