At the time of doing the checkout the page of luma shows me this: 
When I go to the logs specifically in exception that is where it sends me, this line of error appears:
[2018-06-06 16:57:06] main.CRITICAL: Class Magento \ Framework \ App \ View \ Asset \ MaterializationStrategy \ SymlinkaMagento \ Framework \ App \ View \ Asset \ MaterializationStrategy \ Copy does not exist {" exception ":" [object] (ReflectionException (code: -1): Class Magento \ Framework \ App \ View \ Asset \ MaterializationStrategy \ SymlinkaMagento \ Framework \ App \ View \ Asset \ MaterializationStrategy \ Copy does not exist at C: \ xampp \ htdocs \ magento2 \ vendor \ magento \ framework \ Code \ Reader \ ClassReader.php: 19) "} []
I would like to know what to do ...