Encountered 'Server Error' while trying to install GoogleAnalytics plugin

hello,
While Trying to install the code for the Google analytics plugin, everything shut down and all I can see now is the ‘server 500 Error’ page with this-The website encountered an error while retrieving https://www.stylebymolekor.com/wp-admin/. It may be down for maintenance or configured incorrectly.
what did I do wrong and how can I fix the problem? I can’t access my admin/ dashboard anymore but my site homepage is still up.
I am not tech savvy in any way so I really need help on how to fix this problem.
my site is https://www.stylebymolekor.com
Thanks