Yes, because if your character has a negative Wisdom modifier, they don't have a lot of common sense. It's GM decision how high they set the DC at that point, though. I would set it very low indeed, like a 5.
Why would you need to roll a sense motive check on another PC? That's usually unnecessary.
i would say no i mean the other NPC don't know the language and you know he just need to tell you in that language speak in that language we need a private discution so no check needed even for low WIS build, and there's no secret message since you speak in another language and nothing is unclear like a secret message
That has to be the most confusing sentence I've read today. I'm sure you're mising some full stops and quote marks there, but I can't tell exactly where.
But if I understood OP correctly, they didn't even say that their character knew the language that was ultimately used. Two party members knew it, the NPC did not, that's all we have got to go on.
I would make the NPC attempt a fairly easy roll.
I wouldn't, of course, force a PC to do the same.
Often, when a player says they want to do something that I know will be a fairly stupid choice, I ask them to perform an immediate Intelligence check or Wisdom check, depending on the circumstances. Intelligence is usually to remember a fact they'd heard previously or a piece of knowledge their character was made aware of, or Wisdom for intuitive understanding to predict that this might not go well. I'll usually set the DC at 10 for really blatantly obvious stuff, 15 for routine facts they might have missed, or 20 for a difficult check.
Essentially it lets the player have one last chance to realise this probably won't go well, but doesn't intrude on their own power of choice to try it anyway.
In the above example, if two players were discussing how best to kill and eat the third, I'd give the third character a Sense Motive against their bluff, even if they're speaking another language. There's a specific use of Sense Motive to get a DC 20 "hunch" that something's up.
Otherwise, if one character's just trying to have a private conversation in a language the NPC doesn't understand, I'd give the NPC a Sense Motive to check if they're planning something nasty, and possibly change their attitude down one step per the Diplomacy rules since the characters are being openly rude.
Prior to this, I'd call for a Wisdom check from the rude character to give them a chance to avert a social faux pas.
It depends on the situation, really. Standing around in a nobleman's manor at a fancy party, talking with your host, and then suddenly turn to your companion and break into Gnomish? Yeah, Count Evil Von Murderbotham probably isn't gonna take that too well. Chatting with an absent-minded sage in his workshop and start up a conversation in Sylvan? He'll probably just continue rambling on his own topic without even noticing you stopped paying attention five minutes ago. It's up to the GM to adjudicate how the NPC would react.
Yep, I use Intelligence checks as a catch-all for something that wouldn't otherwise be covered by a Knowledge check. I use Wisdom checks for stuff that you could reasonably predict leading to a poor result from cause and effect.
For example, if a player's made a Knowledge check about a monster previously but tries to do something their character would know it's immune to, I'd ask for an easy Intelligence check to remind them of that fact. If they've witnessed the monster displaying an immunity to a certain type of attack before without actually making the Knowledge check, it'd be a Wisdom check instead.
However, there's often significant overlap, and typically I'll deliberately give the player the better of their two stats for the roll. It's a nebulous area of the rules that's intended for GM interpretation, and I'll usually try err on the side of the player when choosing which bonus to use.
I don't mind the GM asking a player to roll to be given a hint or idea. Forcing the player to make a roll so that the PC can be "allowed" to have a "smart" (or even "common sense") idea which the player already came up with seems a little oppressive though. If a GM feels like there's a player with 16 Int coming up with too many genius level ideas for a PC with 7 Int and Wis maybe there are some roleplaying or metagaming concerns to address there, but needing to roll to think of stuff you've already thought of sounds kind of frustrating.
Sometimes the group can think of a way for a player's smart idea to get expressed in the party even if that player's PC is stupid (divine inspiration, "one time at band camp", "Master Algathor once said...", Rain Man has an idea, etc)