Hi Mehrdad, No, they can’t be used interchangeably. “Going to” is for something that people have already decided to do. It is also mostly for more near-term future events. “We’re going to go to the movies Saturday night,” said on Thursday. “Will” is for promises, like a proposal of marriage, and often is used for events further in the future. You also use it when someone is making the decision right after you ask.

'Are you going to marry me?' cannot be used as a way of asking somebody to marry you. Use 'will you marry me?' 'Are you going to marry me?' would really only make sense in a context in which the couple is already engaged, have agreed to marry, but then it looks like the one party might be about to change their mind.

Irene gave a good answer.