Hola. We were supposed to go tomorrow, but we decided to go next week instead. ------ Se suponía que íbamos a ir mañana, pero decidimos ir la próxima semana. •I'm supposed to help her; she's my mom. ----- Se supone que debo ayudarla; ella es mi mamá •They say it's supposed to be better than the last iPhone!-------- ¡Dicen que se supone que es mejor que el último iPhone!

There are several ways! "Suponer(se)" works differently in Spanish. "Se supone que..." and then you put the phrase. (Or "suponer" in another form) >Se suponía que íbamos a ir mañana, pero decidimos que iríamos la semana que viene. But you can use another similar word, "supuestamente". Which would work like... supposedly, I think? But I think we say it more in Spanish (?). >Supuestamente la tengo que ayudar; es mi madre. // Se supone que la tengo que ayudar; es mi madre. Also, I think that, when you say "supuestamente" you can omit the "they say" part. >¡Es mejor que el último iPhone, supuestamente! (But in this case, you can also... omit the supposed part! "¡Dicen que es mejor que el último iPhone!", because you can understand that it's not certain with the "dicen". I guess that's the same in English though...) The good part about "supuestamente" is that you don't need to put too many subordinate phrases. (I hope I helped!)

I was supposed to - Yo tenía que............. / Yo tenía planeado.............