Hello,
1) 502 error? Or what error? Provide screenshot, please.
2) Go to Theme Options > Header builder > edit the connection block and remove newsletter element if you don’t want to show it or edit its settings according to your needs http://prntscr.com/sd56uq
3) Did you read theme documentation https://xstore.helpscoutdocs.com/article/30-base-theme-translation ? From your screenshot I see that you placed your translation to the wrong directory and you will lose it after theme update. Move your files to System or Custom directory, Don’t use Author directory http://prntscr.com/sd58i6
Also, to get the Save button active you need to translate something at least.
Regards