He worked with great commitment for the Children of Mary, a group which supports missionaries, when he was a vicar in the parish of St Peter and Paul in Świętochłowice.

[citation needed] A meeting with Hyacinthe Thiandoum, the Senegalese Cardinal from Dakar, that took place in 1979, during the first pilgrimage of John Paul II to Poland, had a significant impact on Halemba's decision to become a missionary.

After language preparation over several months, he went to Zambia in 1983, where he served for 12 years in the diocese of Mbala (now Kasama),[2] in the Mambwe Mission[3] "Fidei Donum" as a missionary (1983-1993 et 2004–2005).

He had to struggle with difficulties such as malnutrition, a malaria epidemic, lack of antibiotics and vaccines, high perinatal mortality - with the nearest hospital about 80 km away, it was not always possible to bring the patient there on time.

[citation needed] To overcome the obstacles in saving every human life, the missionaries and the local people have undertaken the construction of a charitable hospital in Mambwe, at the periphery of the diocese and country.

Thanks to the administrative assistance of Bishop Adolf Fürstenberg, the financial support of benefactors and the commitment of the local people who contributed with their labour, the hospital in Mambwe was finished in two years.

They were reluctant to use the existing Protestant translation from the late nineteenth century with numerous borrowings derived from Swahili, outdated linguistic forms, and lots of grammatical inconsistencies.

In addition, Fr Halemba edited and published the work of the African missionary, White Father Marcel Petitclair, the Roman Missal in the Mambwe language.

In 2004, he obtained a doctoral degree in theological sciences with his thesis entitled "Religious and ethical values in the proverbs of the Mambwe, Zambia".

From 2010 to 2020 he was responsible for helping the Church in the Middle East (the Holy Land, i.e. Israel and Palestine, Lebanon, Jordan, Syria, Iraq, Iran, Afghanistan, Turkey, Cyprus, Azerbaijan, Georgia, Armenia, Egypt, Ethiopia, Eritrea) and in the Arabian Peninsula (Saudi Arabia, Yemen, Oman, Kuwait, Qatar, Bahrain, United Arab Emirates).

)[18] in frame of the Congregation for Oriental Churches,[19] a committee which unites funding agencies from various countries around the world for the sake of providing better assistance to Christians.

[citation needed] During the genocide of Christians in the Middle East, he hurried to the rescue of the Church affected by war and persecution,[20] especially in Iraq and Syria.

He is the author of the Return to the Roots[21] program (Marshall Plan for the Nineveh Plains),[22][23] which obtained international financial support and enabled the reconstruction of private homes and the infrastructure of the Church in Iraq.

Our way to God" initiative led to the launch of a series of Bible catechesis, based on the tradition of the Church, intended for Arabic-speaking baptism candidates.