Hi Mario,
You actually do not have to add the custom CSS that was provided.
The reason why the rows are shifted to the left is because of the Inline CSS that you have added to the Row specifically margin: 0px
.

There is a setting in the Row where you can set the margin so that you do not have to add it through an inline CSS:

Notice that the right and left margins are set to auto which centers the row. Since you have added margin: 0px
to the inline CSS field of the row, the default margin setting is overridden thus, pushing the entire row to the left.
Hope this helps.