,

many times i come across 3 dots in triangle twice in a verse.

i was told that u have to stop either in first one or second. is it right?

Yes. It's called mu'anaqah.

This means that the reciter should stop at one of the two sets of dots, but not the other. The reciter has their choice as to which of the two sets he/she would like to stop at.

Allah knows best.

jazaak Allah khair sister

yehp the sister was correct

Yes it is written in Quran for the easiness of reciter. These conditions has been set as Prophet Muhammad (PBUH) was used to read the Quran.