What is the best way to deepen understanding of Gurbani beyond just reading the translation?

Respected Ashwani Sharma ji,
Waheguru ji ka Khalsa, Waheguru ji ki Fateh!

In response to your question, the undersigned wants to say that the need is to first understand the basic principle taught by Guru Granth Sahib and live life accordingly.

Guru Granth Sahib teaches this principle, in the very first Pauri of Jap Baani, that one should become a righteous/virtuous person and always remain in His Hukam (Divine Will).

This goal was laid down by the First Guru Person, Guru Nanak Sahib, when, in the first Pauri of Jap Baani, he said:-

ਕਿਵ ਸਚਿਆਰਾ ਹੋਈਐ ਕਿਵ ਕੂੜੈ ਤੁਟੈ ਪਾਲਿ ॥ ਹੁਕਮਿ ਰਜਾਈ ਚਲਣਾ ਨਾਨਕ ਲਿਖਿਆ ਨਾਲਿ ॥੧॥

Therefore, one needs to follow this principle and live a purposeful life. Once a person starts living life, as per Gurbani, then with the passage of time, his understanding of Gurbani will improve because, as per Professor Sahib Singh ji, who has given meanings of all the Shabads in Guru Granth Sahib, the entire Guru Granth Sahib is explanation of the above basic principle.

One can become a righteous/ virtuous person only when one gets rid of vices. Further, once one achieves that and remains in His Hukam, he will be able to achieve the stage of spiritual equipoise (ਆਤਮਿਕ ਅਡੋਲਤਾ) and spiritual bliss (ਆਤਮਿਕ ਆਨੰਦ). Getting rid of vices amounts to achieving spiritual emancipation/salvation in this life itself, as per Sikh principles.

Hope it helps. If you have any further questions, please do ask. If you find any deficiencies, please point out the same, for improvement in future.

Regards,
Your Brother