Learn Portuguese (Portugal): Eu não deixo de arrastar o sofá até que ele esteja no canto. - I do not stop dragging the sofa until it is in the corner.

The phrase até que (until) sets a limit in time. Because the sofa being in the corner is an anticipated event that hasn't happened yet, Portuguese requires the present subjunctive. Esteja is the present subjunctive form of estar.

Why do we use estar (esteja) instead of ser (seja) for the sofa's location?

In Portuguese, we use estar for physical locations of objects or people, even if you plan to leave the sofa there permanently. Ser is reserved for permanent characteristics and origins, but not for where things are placed.

How does não deixo de arrastar translate to 'I do not stop dragging'?

The verb deixar usually means 'to leave' or 'to let', but the specific phrase deixar de followed by an infinitive (like arrastar) means 'to stop doing' something. Adding não makes it 'I do not stop'.

Can I say até ele estar instead of até que ele esteja?

Yes, you can! Using até followed by the personal infinitive (ele estar) means the exact same thing. Both structures are completely natural in European Portuguese, though até que with the subjunctive can sound just slightly more formal or emphatic.