restore plugins crashed my site!

I was attempting to use a Performance plugin to optimize my site and suddenly, the site went down. A 500 Error. But, I was able to go to UpdraftPlus – Restore. All I wanted to do was restore the plugins. I clicked on plugins, then Restore which found my plugins zip in the Dropbox, but it said the file size had changed. Well, I did it anyway, and now the site doesn’t come up at all. What can I do????