"This is the first week of March."
Translation:यह मार्च का पहला हफ़्ता है ।
हफ़्ता and सप्ताह both mean 'week'. हफ़्ता comes from Persian while सप्ताह is a direct borrowing from Sanskrit.
हफ़्ता is more widespread in regular usage while सप्ताह is more formal which means you'll see it more in newspapers, speeches etc. This is true for most words borrowed directly from Sanskrit which are seen to be more formal than their synonyms which are derived from Sanskrit but undergone orthographic changes or their synonyms that are borrowed from Persian/Arabic.
होता is used to denote the 'imperfective' aspect that indicates ongoing/habitual actions. It shouldn't be used in this sentence.
You would use it in sentences like मार्च का पहला हफ़्ता ठंडा होता है where you are saying that the first week of March is cold every year and not just talking about a particular March.