HTTP ERROR 500 after installing child-theme [WordPress] [closed]

In general a 500 Server Error can be solved (or at least be correctly identified) by looking at php logs. If you are on a shared hosting you should have something in your hosting’s control panel to check the logs (look for Error messages), if you are self-hosting on your own vps you can usually find the logs in the /var/log directory.

This said, the current theme in WP is stored as two entries in wp_options, which are template and stylesheet. Name back the theme directory like the original one, write down the directory name of the original theme, and put it as the field value for wp_options.template and wp_options.stylesheet. At this point WordPress is, if you haven’t touched anything, be in the same state as before you child-theme’d.

Refer to the first paragraph of my answer and edit the answer with the php error so we can look at it.