"I trust my son."
Translation:Jag litar på min son.
I'm curious, why is "på" required? Would "litar" translate into something else without it?
It's one of those annoying particle verbs - it always takes a på. It doesn't translate into anything else if you remove it - it just becomes nonsense.
No, that means that you believe in him. And you have to use the present tense tror in the sentence.