Learn Polish: Jutro będę malował swój stary pokój. - Tomorrow I will be painting my old room.

będę malował is the imperfective future tense. It focuses on the ongoing process or duration of the action ("I will be painting"). If you wanted to emphasize that you will complete the job ("I will paint and finish"), you would use the perfective future tense, which is a single word: pomaluję.

Why does malował look like a past tense word if the sentence is happening tomorrow?

To build the imperfective future tense in Polish, you combine the future tense of "to be" (będę) with the third-person past tense form of the main verb (malował). Because it uses the masculine past tense form, we know the speaker is male. A female speaker would say będę malowała.

Why does the sentence use swój instead of mój for "my"?

swój is a special pronoun that means "one's own." In Polish, whenever the subject of the sentence (in this case, "I") is also the owner of the object being acted upon (the room), it is much more natural to use swój instead of the regular possessive word like mój.

Since the room is the direct object being painted, shouldn't stary pokój change its ending for the accusative case?