URGENT! everything is broken!

hi,
I’ve been experiencing a slow site and I’ve tried several solutions I found online using plugins such as free-cdn.1.1.2 , w3-total-cache.0.9.4 and wp-fastest-cache

As I am new to this I probably managed to (i think) destroy my clients site.

https://thewandernotes.com

I’ve tried to change themes and delete the plugins but the situation is still the same. nothing shows up!!! I have enabled a “coming soon” plugin/message so the website wont show up until I fix it.

please let me know you can help me! it’s really urgent!

p.s. I have a backup of the site but it is not very recent. I don’t want to lose any new added posts or images. pls help!!