I wanna know too of the estimation of age gap.

It was interesting to kno that she is older in real life but she isplaying a younger role than him :)

 Mary:

You can see their date of birth on the marriage registration. The ML was born October 25, 1987 and the FL March 17, 1993. 

So he is 5 years and 5 months older than her.  During the fire 13 years ago he was 23, and she was 18 years old.

Yes. This info is from Ep 4.

So the next question is Has ML really saved the FL...

 honey_boo:

and my question is are they in love? Or are they in a situationship? im so confused by their dynamic

I don't think they are in love. They seem to be attracted to each other, but also suspicious. She seems a bit scared of his powers, but is even more scared of her "mother".  And he is really fascinated/intrigued by why he can interact with her while time travelling. So right now they are both using the other.

They will probably fall for each other, though.  Going by the preview for episode 5 that kiss definitely did not leave them cold.

 Mary:

You can see their date of birth on the marriage registration. The ML was born October 25, 1987 and the FL March 17, 1993. 

So he is 5 years and 5 months older than her.  During the fire 13 years ago he was 23, and she was 18 years old.

So they are the same age now, when he is back 

During the 13 years ago fire, ml and fl had so much free time do they could have jumped together from the school building. Plus if the ML threw the FL through the window he could managed to get to the present, where the clock wall had already fallen, while he was saving the FL in the past...

So what was the exact moment that the kid saved the ML. And ML didn't manage to...

So the connection is destiny only.

The ML met the FL in order to save her in the past.