"It remains to be seen who wins."
Translation:Rămâne să vedem cine câștigă.
How can I know that i have to use "vedem" here? Any logic behind this? Or it's just an expression?
A more accurate translation is "Rămâne de văzut cine câștigă".
The problem with "rămâne să vedem [...]" is that in some specific contexts it could have a different meaning, more along the lines of "we still have to do/take care of [...]", i.e. it would imply there's an action plan on our part.
Are there any rules for when sa or se should come before or after the verb. This lesson has contained examples of both! Also what is the grammatical difference between sa and se?
I think the two have nothing in common. Sã is a conjunction used with the subjunctive and always precedes the verb. Se is a reflexive pronoun, a bit similar to "himself," and can be used for impersonal constructs.