For the T-Shirt challange , I try to import the contacts_to_import.csv file which were downloaded from the challange page but I got the folowing error 
contacts_to_import.csv
There was a problem uploading the CSV file. Try again, or choose another file.

Create custom objects, fields, and relationships challange,  check the button didn't work

Once I complete and click the challange check button , It didn't work  or response , Once I refresh the page I am unable to login the challange again.

According to Lightning Components Developer’s Guide (https://developer.salesforce.com/docs/atlas.enus.lightning.meta/lightning/qs_aotp_app_step2_cmp.htm (https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/qs_aotp_app_step2_cmp.htm))

I am trying to create a new component, form.cmp. but I am unable to save form.cmp , I already Register a Namespace Prefix and Enable Lightning Components checkbox 

I got the following error , please help me on this 
FIELD_INTEGRITY_EXCEPTION
Failed to save undefined: No TYPE named apex://namespace.Expense__c found : [markup://kuhan:form]: Source

when I change the namespace to kuhan(kuhan is my namepace) I got the following error
FIELD_INTEGRITY_EXCEPTION
Failed to save undefined: No TYPE named apex://kuhan.Expense__c[] found : [markup://kuhan:form]: Source
 

For the T-Shirt challange , I try to import the contacts_to_import.csv file which were downloaded from the challange page but I got the folowing error 
contacts_to_import.csv
There was a problem uploading the CSV file. Try again, or choose another file.

According to Lightning Components Developer’s Guide (https://developer.salesforce.com/docs/atlas.enus.lightning.meta/lightning/qs_aotp_app_step2_cmp.htm (https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/qs_aotp_app_step2_cmp.htm))

I am trying to create a new component, form.cmp. but I am unable to save form.cmp , I already Register a Namespace Prefix and Enable Lightning Components checkbox 

I got the following error , please help me on this 
FIELD_INTEGRITY_EXCEPTION
Failed to save undefined: No TYPE named apex://namespace.Expense__c found : [markup://kuhan:form]: Source

when I change the namespace to kuhan(kuhan is my namepace) I got the following error
FIELD_INTEGRITY_EXCEPTION
Failed to save undefined: No TYPE named apex://kuhan.Expense__c[] found : [markup://kuhan:form]: Source