Lenga spent his one-year novitiate in the Marian Order, then a week visiting a monk, his spiritual mentor.

Lenga was appointed Apostolic Administrator of Kazakhstan and Central Asia, and Titular Bishop of Arba on 13 April 1991.

Diocesan bishops, who due to ill health or some other compelling reason are not fully able to perform their duties, are urged to submit their resignation.

Lenga was appointed as the successor to the apostolic administrator of Atyrau, Bishop Janusz Kaleta.

On 10 June 2019 Lenga, along with cardinals Raymond Leo Burke and Jānis Pujats, with Kazakh bishops Athanasius Schneider and Tomasz Peta published a 40-point "Declaration of Truths" claiming to reaffirm traditional Church teaching.