Hello,
If even backend is slow then you need to contact your hosting provider to find the reason of this issue.
To change the newsletter block: 1) Enable VC editor for your static blocks http://xstore.helpscoutdocs.com/article/47-static-blocks 2) edit the content according to your needs http://prntscr.com/hkcvsq To change the background use design tab http://prntscr.com/hkcwtz
Regards
