tid = time, as in the dimension that slowly passes and causes you to age
gång = time, as in once, twice, thrice etc
[Den här gången] is the first place, you can tell that from the fact that you could replace it with just 'nu'. You can have even longer things in the first place sometimes, like whole subclauses for instance.
Oh and it's måste that is the verb, 'vinna' is just an infinitive and doesn't count for the V2 rule.
Do we need här in this sentence? Is there another word that can imply about something that's happening now..
'this' is den här or denna, so you could have said denna gång – but that sounds a lot more formal.
den här gången and this time means 'at this occasion' or something similar, not just that it is happening now. For instance we have tried before 2 times and lost, now this time we must win.
Does the V2 rule mean that "Den här gången vi måsta vinna" is wrong? Would this be putting the verb in "third place"?