How do you get paras to fall in love?

I am really struggling to get my para and another to fall in love. I get the interaction going (all positive), get from time to time a flirty one, get +1 friendship... And nothing. The relationship is still at the acquittance 1. At one point, I tried to get them in a restaurant (a.k.a like a date) but unfortunately there isn't an option for them to do activities together. I have read it is supposed to be a +3 for a romantic relationship, but how do you get there?