El domingo pasado, yo iba con mis amigos al cine.
What is wrong?
This is the difference between the Imperfect (I was going, I used to go, I went = in the sense that you were in the "middle" of it = en route, so to speak
and
The Preterit (I went, I DID go), action completed.
Imagine the imperfect like waving lines = ~ ~ ~, or action in progress, as if you were filming with a movie camera.
Imagine the preterit like / / / or a camera taking ONE photo.
So rather than saying "Last Sunday I was ging with my friends to the movies..." which implies that you never arrived there; maybe something else interrupted your going.
BUT
El domingo pasado, yo fui con mis amigos al cine. = meaning that you WENT, or DID go.
Please ask any questions if there is still something you don't understand. I have lots of information on the difference between the Imperfect and the Preterit.
Sra
El domingo pasado, yo iba con mis amigos al cine.
This says
Last sunday, I was with my friends at the movie theater.
It would be better if it said
El domingo pasado fui al cine con mis amigos.
Last Sunday I went to the movie theater with my friends.