Ok, in order to close the gate with elder sign i need to move in the R'lyeh this turn and get out and close it next ?
If yes that's what i do,hope i don't get stuck in another dimensions 
Will i need to fight monsters outside when i get out ?
And if it matters i choose the +2 sanity encounter (sanity can't be raised above initial value,can it ?).
You're gonna be screwed for awhile, actually. Delayed for one turn, then you have to move to right side of R'lyeh next turn, and THEN you can leave (if you weren't screwed by encounters). And yes, definitely get your skills ready for encounters/when you leave.
Wow, five pages while I was asleep...
Tyberix, you should get some fighting/lore skill before you get out of that gate. You need to pass a -3 check, preferably without wasting precious clues.
As for the ritual, we'd better stop it before Tyberix gets out of R'Lyeh, we don't want him - or anyone else - against that warlock right now. We can trade spells, so anyone with spells they can spare should hurry to the French Hill. 5 spells is a lot, so it'll hurt, but I think it's our best bet. I, myself, could offer both of my spells, but I'd prefer to use rather useless spells on this.
Edit: We have 9 spells all together. If anyone could make a stop in the magic shop to get some 'useless' spells, that would help a lot. Anyway, I'll offer my 'find gate', and 'shrivelling' if it's needed.
Actually, you misread it. It's 4 Spells if 5 or more players; not 5 spells. XD
Oh right, didn't notice the elder sign, sorry.
Still, I think it's best to shut down that ritual ASAP. We don't know what might need our attention next turn(s). I can get to the French Hill this turn, anyone else with spells to spare? Or wait a turn and buy one first?
Edit: I hate to make the game more difficult for us, but I hate cheating even more:
MONSTERS GUARDING GATES
During the turn he returns to Arkham from an Other
World, an investigator does not have to evade or fight
any monsters in the gate’s location. This rule only
applies during the turn he returns to Arkham; in subsequent
turns, if the investigator remains in the location,
he must evade or fight any monsters there as normal.
So even if he doesn't leave, he still has to fight the turn after he comes out of the gate.
It still gives him a breath for at least one turn; and he has Fight, Knife; hopefully we can take down that rumor before bad things happen. So he'll be exempt from the Arkham Encounters phase when he is able to leave the gate that turn, and the next turn after he leaves the gate he can either move or fight the warlock; hopefully the rumor will be gone by then...