Apaurusheya means not man-made. Veda mantras are eternal. They are revealed through Rishis. 

According to Krishna Yajurveda, Indra incurred the sin of brahmahatya when he killed Trishiras. He divided the sin into three parts and gave them to the earth, trees, and women to get relief. In return, women received the boon of not incurring any sin by being physically intimate with their husbands only for pleasure. Until then, physical relationship was permitted only for procreation. The sin of Indra would exist in the bodies of women during their periods. They will have brilliant children if they observe certain rules during periods.

Rigveda  1.18.7 - sa dhīnāṁ yogaṁ invati - He promotes yoga of thoughts.1.30.7  - yoge yoge tavastaraṁ vāje vāje havāmahe - In each yoga we invoke Indra. 10.114.9 - kaś chandasāṁ yogaṁ ā veda dhīraḥ - Who knows the yoga of the meters? The term yoga is used here to mean unifying.

In Vedas, you will find several Devas being described as the Supreme God. It may sound confusing to the layman. Upanishads settle this by declaring that there is only one supreme God called Brahman and the others are just his different names and manifestations.

A large number of Vedic texts are available at https://archive.org/search?query=vedas

Atharva Veda contains many mantras and procedures for curing diseases.