Learn Hardcore Spanish (Spain): En mi cuarto, aprendo español cada día.

Both cuarto and habitación can mean "room." Cuarto is a bit more informal, but in everyday speech in Spain, it's commonly used to refer to your bedroom. Habitación is perfectly correct too, though it might sound slightly more formal or general (like a hotel room).

Why is aprendo (simple present) used here rather than estoy aprendiendo (present continuous)?

In Spanish, the simple present tense (aprendo) can express habitual actions—things you do regularly. Estoy aprendiendo would emphasize the ongoing process of learning at the exact moment. Since this sentence talks about a routine (learning Spanish every day), aprendo is the natural choice.

Is there a difference between cada día and todos los días?

They mean essentially the same thing ("every day"). Cada día literally translates as "each day" and todos los días as "all the days." In everyday Spanish, you can use either interchangeably without changing the meaning.

Could we say Aprendo español en mi cuarto cada día instead?

Yes, the sentence remains correct. Word order in Spanish is flexible. Starting with En mi cuarto adds emphasis to the place where you do the learning, but placing it later is also perfectly fine.