Learn Spanish (Latin America): El aprendiz corta el metal desde hace tres horas. - The apprentice has been cutting the metal for three hours.

In English, we say "has been cutting" for an action that started in the past and is still happening. In Spanish, because the apprentice is still cutting the metal right now, you simply use the present tense corta alongside the time phrase desde hace.

What is the literal meaning of desde hace in this sentence?

Literally, it means "since it makes." Desde means "since," and hace comes from the verb hacer (to make/do), which Spanish uses to measure passed time. Together, desde hace plus a time period means "for that amount of time" when the action is still ongoing.

Could I put the time phrase at the beginning of the sentence instead?

Yes, absolutely! You can say Desde hace tres horas, el aprendiz corta el metal. Putting the time phrase at the beginning of the sentence is very common and just adds a little more emphasis to how long the action has been happening.

The word aprendiz ends in "z". How do I know its gender, and how would I talk about a female apprentice?

Nouns ending in "z" can be masculine or feminine, so you have to look at the article. Here, el tells us this is a male apprentice. To talk about a female apprentice, you usually just change the article to the feminine form: la aprendiz.