First you need to check theme is applied or not. You can check your current theme by **ctr + U**, you can see current theme path in **.css** and **.js** file.

In your case **Magestore/Sample** display in **.css** and **.js** file path. If display it, theme is set properly.

Run below command 

>     php bin/magento setup:upgrade
>     
>     php bin/magento setup:static-content:deploy
>     
>     php bin/magento cache:clean

Now you can see your changes.

Let me know if you have any query.