I have just install umbraco 7.13.2 version and running website using VS 2017. When i run first time it's throwing error

"The type or namespace name 'Image' could not be found (are you missing a using directive or an assembly reference?)" because  gallery.cshtml file having image class reference, so i have added "@using System.Drawing" after that i build website and getting multiple errors- 
1) Severity Code    Description Project File    Line    Suppression State
Error   CS0307  The property 'IPublishedContent.Children' cannot be used with type arguments    UmbracoCMS  E:\UmbracoCMS\Umbraco\PartialViewMacros\Templates\Gallery.cshtml    35  Active


2) Severity Code    Description Project File    Line    Suppression State
Error   CS1061  'Image' does not contain a definition for 'Url' and no extension method 'Url' accepting a first argument of type 'Image' could be found (are you missing a using directive or an assembly reference?)   UmbracoCMS  E:\UmbracoCMS\Umbraco\PartialViewMacros\Templates\Gallery.cshtml    48  Active

3) Severity Code    Description Project File    Line    Suppression State
Error   CS1061  'Image' does not contain a definition for 'GetCropUrl' and no extension method 'GetCropUrl' accepting a first argument of type 'Image' could be found (are you missing a using directive or an assembly reference?) UmbracoCMS  E:\UmbracoCMS\Umbraco\PartialViewMacros\Templates\Gallery.cshtml    49  Active

4) Severity Code    Description Project File    Line    Suppression State
Error   CS1061  'Image' does not contain a definition for 'Name' and no extension method 'Name' accepting a first argument of type 'Image' could be found (are you missing a using directive or an assembly reference?) UmbracoCMS  E:\UmbracoCMS\Umbraco\PartialViewMacros\Templates\Gallery.cshtml    49  Active

Please help me out to get corrected this or get base code library to check this.