Use your ftp program or your cPanel to access the folders and disable the problem plugins by renaming them.
Simply put an underscore in front of the name to disable them, in your case the cache and slider, maybe more.
That should get you started again.

Yep use FTP, login and I suggest disabling all the plugins using the method Joseph mentions. Look at your site and see how it looks, if the errors are gone it is a plugin. Next step is to enable the plugins one by one and testing the site after removing them. Just remove the _ in front of the name to enable them again. When it breaks you have your problem plugin!

Fix it from the Cpanel or FTP and also update to the latest WordPress version. Always make strong password for your WordPress sites so that they should not be hacked.

One error message that'll cause you to pull your hair out, along with many hours of frustration, is headers already sent. What headers already sent means is that some output has already been sent to the browser, so no changes can be made to the HTTP headers because they were already sent with the original output. HTTP headers carry information about the client's browser, the requested page, the server, sessions, cookies, etc.

A "headers already sent" error message typically confuses people because they tend to look in the wrong place for its cause. The important thing to know is to look where the output starts, which is buried within the error message (output started at /home1/rhuq/public_html/nosdaf.com/wp-includes/bookmark.php:437).

Login to your cPanel, look for the bookmark.php file, and download the file. Open the file in a "good" text editor, like Notepad++, or one that will show you line numbers. Start looking at, or just before, line #437. It may be something as simple as a semi-colon ";" or a closing bracket "}" missing from the code. I have looked at my bookmark.php (just downloaded) file and mine only contains 415 lines. There's a good chance that this file is corrupt, possibly by one of your plugins.

As mentioned in a previous post, rename or delete your plugins, and once your site is back up and running, activate them one at a time. It may or may not be a plugin error, but this is a step you should consider taking. If this is a new site, and it's the first time looking at it, maybe it's a PHP configuration file setting. Check with your hosting provider on that.