Learn Spanish (Latin America): Yo voy al supermercado pronto.

In Spanish, whenever the preposition a (to) is followed directly by the masculine word for "the" (el), they must combine into the single word al. Since supermercado is a masculine noun, we have to say al supermercado instead of a el supermercado.

Does voy mean "I go" or "I am going"?

It can mean both! The Spanish simple present tense is very flexible. Depending on the context, yo voy can mean a general habit ("I go") or an action happening right now or in the near future ("I am going"). Because of the word pronto (soon) in this sentence, "I am going" is the most natural translation.

Do I have to include yo at the beginning of the sentence?

No, it is completely optional. Because the verb form voy uniquely means "I go", the listener already knows who is doing the action. Native speakers frequently drop the yo and just say Voy al supermercado pronto.

Can I put the word pronto somewhere else in the sentence?

Yes, Spanish word order is quite flexible. While putting pronto (soon) at the end is very common, you could also put it right after the verb and say Yo voy pronto al supermercado. Both sound natural and mean the exact same thing.