How do shut the gate?

In the KVATCH oblivion gate, the same rules apply but since it's the first gate opened there shouldnt be any problems. If I remember correectly in this particular gate of oblivion you need to enter a smaller tower going up the staircase (maybe needing to activate a lift called "corpse masher" the lever should be near by or simply press on the lift itself), and finding a "caged prisoner" there is also a daedra guarding the cage you'll need to kill him and loot the key on his body. Then you may need to press a lever opening a large black gate (maybe not tho, if not the key should open the next passage). After speaking with the caged prisoner he'll tell you to find the sigil stone and to leave him behind. Go back down the staircase to reach the lift but DO NOT re-activate it there should be a door leading to the "wastes of oblivion" enter it. The rest is pretty vague to me in my memory so it should be like any other gates. If you pressed a lever that "opened a door elsewhere" you should see the black gates opening then you should see a larger tower behind the gates enter it. Make your way past the "rending halls" up the paths leading up and all the way to the sigilum sanctus (or something). If I remember correctly the key found on the dead daedra opens the sigil door. Then simply kill the remaining daedra and grab the sigil stone to close the gate. It is rather far in my memory but since it's the first oblivion gate in the game it shouldn't be too difficult....look for the large tower "tower portal" door, then the rending halls, then go up the paths, then into the sigilum sanctus (or something) , and finally taking the sigil stone....have fun!!

You hsve to go in the big tower to the north of the gate.

In any oblivion gates your goal is to reach the "sigilum sanctus" (or something), and take the sigil stone that opens/closes the gates. As soon as you enter ANY oblivion realms do a quick scan of the place and try to notice a large tower (in some cases there might be many) and try to enter it. The name of the correct door that leads to the sigil tower should be called "tower portal". Once inside the tower if you hear a "pulsating" noise then you are in the right tower if not keep searching the tower for another exit. Then you need to find a door that is called "rending halls" (should always be in the sigil tower's first floor). Next you should ALWAYS take paths that lead UP in the sigil tower, if you find a path leading down DO NOT take it, instead search for a door that either leads to another area or that leads up. Next changes by the realm you are in (there are several oblivion realms said 1 for every daedric prince so around 16 different maps in oblivion), you will either find doors leading to the "dead halls" or "dark salvation" etc. They are the next doors leading you forward. After that it's in and out of the halls and the stairways. When you reach the door called "sigilum sanctus" (or something) you'll need to climb "red bone" staircases fighting a few more daedra and on top there it is the sigil stone simply get close to it and grab it. Sigil Stones are "leveled" items meaning if you grab one at level 2 it will be considerably weaker than if you grab it at level 17+. But since there are 50 oblivion gates it's a great way to level up !!

Get in the top of the big tower and take the sigil stone.