How does meat become halal?

Halal meat is better since it meets Islamic religion teachings.   Unless you are a Muslim it makes no difference.   The scientist said that most of viruses and microbes are in the...

yes.

they slaughter it by saying certain words that praises the God, and i think its preferably slaughter by hand not machines

Aldi meat could be halal (allowed for Muslims to eat) or not. It depends it is of what animal meat. Refer to question below on Muslim allowed (or halal) meat, then check about the specific Aldi meat...

Not all of it. Some stores will say that they sell halal meat. It's good to ask at the store.