Hello @M72561,
To downgrade WooCommerce, please walkthrough below steps:
- Deactivate WooCommerce from Plugins > Installed Plugins. Make sure not to delete WooCommerce plugin.
- Download WooCoomerce 3.4.0 from following source. https://wordpress.org/plugins/woocommerce/#developers
- Login to your hosting through FTP or Hosting Panel
- Navigate under wp-content/plugins/woocommerce directory
- Replace the existing files with that newly extracted
- Activate WooCommerce from Plugins > Installed Plugins
You can get started with FTP using following article:
https://www.tipsandtricks-hq.com/how-to-use-filezilla-with-wordpress-8956
To backup WordPress you can take a look at following article:
http://www.wpbeginner.com/plugins/how-to-create-a-complete-wordpress-backup-for-free-with-backwpup/
The JS error on the other hand is coming from LinkedIn. You must have added a LinkedIn code or a 3rd party plugin is causing it. You could try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Please let us know how it goes.