If a column was added to the sample table by yourself, you and team Administrators have the right to delete it.
If the column was not created by you and you are not a team Administrator, meaning you cannot delete columns created by other team members, you still have a possibility to make them invisible. Click the Columns button and hide the column in a sample table by clicking the eye icon. When the eye is crossed the column is not visible.
To delete a column, click the Columns button, select the column you want to delete and click the trash bin icon.