Hello,
I have checked your website, and I am able to access the WordPress admin dashboard without any issues now.
See the screenshot for clarification:https://postimg.cc/H8z7XNc2
Based on the screenshot you shared, the error was caused by the PHP memory limit being exhausted while processing a request, which may have occurred after deactivating the slider plugin.
Since the admin area is currently accessible, it appears that the issue has been resolved.
If you encounter the same error again, ensure that the PHP memory limit is set to at least 512 MB, as insufficient memory can lead to this type of fatal error.
Best Regards