The first gāthā of Pucchisūṇaṁ / Pucchisunam is a respectful opening question in which Ārya Jambu asks who that महान soul is, who proclaimed the incomparable and truly beneficial Dharma. In simple meaning, he is seeking to know about Bhagwan Mahāvīr and His supreme spiritual teaching. ( jainknowledge.com)

Simple arth: “Who is that great one who revealed such a pure, श्रेष्ठ, and truly welfare-giving path?” This line expresses bhakti, curiosity, and reverence toward the Tīrthaṅkar’s teaching. It is an introduction to the praise of Bhagwan Mahāvīr’s keval-jñān, keval-darśan, and śuddha cāritra. ( jainknowledge.com)

If you want, I can also explain the first gāthā word by word in simple Gujarati or Hindi.