What is one of the major roles district courts play in the federal judiciary

District Courts are part of the Federal Judiciary System.

It works as a "middle man" between state courts and the Supreme Court, and also can rule on some cases regarding Constitutional Matters, or when the United States is a party, for example.

Criminal and Civil matters can be trialed in these Courts, and it's a very important part of the US Judiciary System.

what are local authorities doing to fix the problem

explanation:

b) the confederacy had to pay all union war expenses.