I’m still confused did they die at the end or not (after they fell in the lake)

I think it's up to interpretation. If they did or didn't is up to you. I wasn't very satisfied with it either, lol. I just choose to believe they survived. Maybe getting sick. They've survived worse, I'd think falling in the freezing water would be an incredibly ironic way to go, considering XD

Like the other person has said, they've both survived worse. That scene where they're both underwater takes us back to the first time jooha saved dooshik from drowning. And the bittersweet moment when they both look at each other teary-eyed like that implies (to me atleast) that the memories came rushing back in.