"I am not waiting for the last car."
Translation:Já na poslední auto nečekám.
Why couldn't you say 'Ja necekam pro posledni auto"? Why do you have to use 'na'?
Because that's the preposition the verb requires. You have to learn that. Different verbs use different prepositions in different languages.
With the demonstrative "to poslední" you are emphasizing it is really that particular last car so I would use that for "that last car". English most often requires an article in "the first/the last something", while in Czech it is just "poslední něco". Just poslednínis specific enough so no demonstrative is necessary.