How do I stop this attack on my wordpress site?

My wordpress webstore which is hosted on hostinger is being attacked intermittently and is going down and up. I received an email prior to the attack asking me to send money to a bitcoin address or the site will remain under attack. I didn't respond and am trying to fix this.

When I try to access my website, I get the following error:

"Error establishing a database connection"

So, then I went into Hostinger and tried to connect to phpmyadmin which connects for a few seconds and displays this error:

" mysqli_real_connect(): (HY000/1226): User 'u223395032_vYqof' has exceeded the 'max_user_connections' resource (current value: 50)"

I've ensured I have a firewall running on my wordpress site through a wordpress plugin, and also have the option to prevent brute force attacks enabled. What else can I do here to stop this?