"He is selling her horse."
Translation:On prodává jejího koně.
Aren't the imperfect verbs used to describe doing something repeatedly? Or can they be used to specify an action at some point in the future as well? What i mean is would it not be better to use the perfect verb here prodat (so prodá) as he is only selling the horse once (but right at this moment)? Or by using the imperfect verb prodavat does it mean he is either selling it repeatedly OR he is selling it once but at some unspecified point in the future?
Um, nope. The imperfective (not "imperfect") aspect shows the action is not finished, whereas the perfective (not "perfect") aspect expresses a completed action. This can create a secondary distinction between things happening once or repeatedly.
In the present tense, the only possible aspect is imperfective, because nothing can be completed in the present - the present is always ongoing, unfinished. You can't have sold the horse NOW - you either sold it in the past (even if just a second ago) or will have sold it in the future. In the present, you're always in the process of selling it.
Hence "prodává koně" (imperfective) is the only present tense. As soon as you change the aspect to perfective, it automatically becomes the future tense: "prodá koně" - "he will sell a/the horse".
- past, perfective: Prodal koně. - He sold a/the horse, he succeeded at selling it, this is referring to the moment of completing the (trans-)action.
- past, imperfective: Prodával koně. - Referring to the process of selling, this will usually be rendered as progressive: He was selling a horse.
- present: Prodává koně. - only imperfective
- future, perfective: Prodá koně. - He will sell a/the horse, referring to the completed transaction.
- future, imperfective: Bude prodávat koně. - Referring to the future period/process of selling a/the horse.
It all becomes more obvious with more exposure. It's a whole different mindset than the tense system in English.