Hello,
I'm Luiz, very used to work with Excel, Website, HTML, CSS, Wordpress.
A alrealdy built more than 10 websites, from static pages until e-commerces.
Now I'm working in a company as System Analyst, chating with clients, making some system manuals, some data analyse using Excel and developing internal applications.
To improve your website the first thing we need to do is contract a SSL certificate, depending on your hosting you don't need to spend money on it, you can use a free SSL certificate, now as Let's Encrypt.
This error I think is something related with database communication.
I hope we can work together.
Sincerely,
Luiz Serpa