In plain words
If You think I am able to behold it, Lord, then O Lord of Yoga, show me Yourself, imperishable.
Word for word
If You think, '[it is] possible for that to be seen by me', O Lord, then, O Lord of yoga, show me Yourself, the imperishable.
मन्यसे यदि तच्छक्यं मया द्रष्टुमिति प्रभोयोगेश्वर ततो मे त्वं दर्शयाऽऽत्मानमव्ययम्
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam· bhāṣya
मन्यसे चिन्तयसि यदि मया अर्जुनेन तत् शक्यं द्रष्टुम् इति प्रभो, स्वामिन् , योगेश्वर योगिनो योगाः, तेषां ईश्वरः योगेश्वरः, हे योगेश्वर । यस्मात् अहम् अतीव अर्थी द्रष्टुम् , ततः तस्मात् मे मदर्थं दर्शय त्वम् आत्मानम् अव्ययम् ॥ ४ ॥
In plain words
"You think" means: if you judge in your own mind that this can be seen by me — by Arjuna — that it lies within my power to behold. "Prabhu" is master. "Yogeśvara": the yogas belong to the yogin, and the lord of those yogas is Yogeśvara — so, Lord of yoga. And because I want this seeing more than I can say, "therefore" — for that very reason — "show me," show it for my sake: yourself, the Self that never wears away.
Close to the Sanskrit
"You think" — you consider — "if" it can be seen "by me," by Arjuna, "that" is "possible to see" — thus. "O Prabhu" — O master. "O Yogeśvara": the yogas are the yogin's; the lord of those is Yogeśvara — O Lord of yoga. Since I am exceedingly a petitioner to see, "therefore" — for that reason — "to me," for my sake, "show, you, the Self, the imperishable." || 4 ||