1.-I was singing on stage..............yo estuve cantando en el escenario..
2..-she was swimming at the beach.............. Ella estuvo nadando en la playa.
3..- your you were running in the field..............Tu estuviste corriendo en el campo
4.-we were in the theater acting......................nosotros estuvimos en el teatro actuando
5.-He was dancing at the concert..............El estuvo bailando en el concierto
6.- we were walking all day, yesterday........nosotros estuvimos caminando todo el dia ayer 
7.-he was listening the class of the tescher.........El estuvo escuchando la clase del maestro
8.-she was cooking fried fish..........ella  estuvo cocinando pescado frito
9.- He was driving his car ..............
Él conducía su automóvil
10.-she was reading his book of short stories........ella estaba leyendo su libro de cuentos


* Estructura:
Hay dos formas GENERALES de expresar una oración en pasado y son:
1° subject + main verb in past + complement + adverb of time.
I played the guitar for a concert yesterday.
2° subject + adverb of frequency + main verb in past + complement.
She never sang at the opera.

sing (= cantar) ----> Past: SANG
1. We sang as we walked.
2. My teacher sang a very nice song last week.
3. Marco sang badly at the concert, everybody wanted him to leave.
4. Rosa sang all the night until she went to sleep.
5. Ricardo and Rafael sang for Sandra a romantic song.

play (= jugar, tocar un instrumento) ----> Past: PLAYED
1. I played soccer with a very good team, so we won.
2. She played the guitar but then she broke her arm.
3. Rosario played basketball with some of her friends last night.
4. He played on silently.
5. José played the piano and gave us a great concert.

work (=trabajar) -----> Past: WORKED
1. We worked at that restaurant once.
2. They worked all the night to get the house sold for the next day.
3. We worked very hard on this so we cannot give up at this point.
4. Jorge worked on his project with his sister's help.
5. Raúl worked in that office but then he got hired in another company.

study (= estudiar) -----> Past: STUDIED
1. I studied maths with my teacher's help.
2. Rosa studied science but then she changed her career for engineering.
3. They studied so hard to be where they are now.
4. Saúl sutied all the night for the test.
5. She studied a little bit last night that's why she got that low score.