You cannot "return to the old update". You can downgrade to an earlier operating system if that is what you are speaking about, but doing so involves having to backup your OS, then completely erasing it and then installing a new OS and your saved files. Not something I would recommend. Instead, I suggest that you provide the information requested above and specifically what is happening with those "glitches" you mention. Finally, I strongly recommend downloading and installing the app EtreCheck. Then run it, allowing full disk access and then post the results below under Additional Text. This report will provide an extensive view of your Mac's system, which we can evaluate and offer recommendations to fix your problem.