so what would "the horse plays" translate to? Isn't "spielt" the plural for "plays"? Therefore "the horse plays" should be correct too?
German doesn't have a continuous aspect. Both "The horse plays" and "The horse is playing" translate as "Das Pferd spielt". This doesn't have anything to do with singular or plural.
How does the verb conjugation for simply nouns, like 'Das Pferd'? ich spiele, is for the 1st person singular, but if it is just a noun doing something what is it? example. the horse(noun) plays