HTTP Error 500.19 - Internal Server Error Code 0x800700b7

HTTP Error 500.19 - Internal Server Error

The requested page cannot be accessed because the related configuration data for the page is invalid.
Error code: 0x800700b7
Config Errpr: Config section 'system.web/pages' already defined. Sections must only appear once per config file. See the help topic <location> for exceptions

Config Source:
59:     </siteMap>
   60:     <pages theme="DarkOrange" validateRequest="false" controlRenderingCompatibilityVersion="3.5"  clientIDMode="AutoID">
   61:       <namespaces>

Can someone help me with a solution on this Error

did you change your theme name?

try to upload unmodified web.config file to your nopCommerce files root.