Learn Spanish (Latin America): Hay que caminar derecho hacia la plaza. - You have to walk straight towards the square.

Hacia means "towards" a direction, while hasta means "until" or "as far as" a limit. Caminar hacia la plaza means you are walking in the direction of the square. If it said hasta la plaza, it would mean walking all the way there and stopping exactly at the square.

I thought derecho meant "right". Why does it mean "straight" here?

This is a very common mix-up! Derecho (ending in -o) means "straight" or "straight ahead" when talking about directions. The word for the direction "right" is derecha (ending in -a), usually used in phrases like a la derecha (to the right).

Why does this sentence use Hay que instead of Tienes que for "You have to"?

Hay que is used to talk about general rules or things that need to be done by anyone, without pointing to a specific person. It translates closer to "One must" or "It is necessary to". If you wanted to tell a specific person "You have to", you would use Tienes que.

Could I use a instead of hacia in this sentence?

Yes, but the meaning changes slightly. Caminar a la plaza just means "to walk to the square", focusing on the final destination. Caminar hacia la plaza specifically means "to walk towards the square", focusing on the physical direction of your movement.