handyman my asre
you want an electrician
Light fittings have more wires in them than you might expect, and it is very common for inexpert people to accidentally connect them as a fuse-blowing device. They are live even when the switch is off.
btw if you are getting metal switches, it is vital that they are earthed and the earth is tested. Some houses, especially wired in about 1970 or earlier, may have no earth on the lighting circuit and must not have metal light switches or metal light fittings.
A single-gang switch turns on one light. A two-gang switch turns two lights on and off separately. E.g. you have a light at each end of your living room, so you get a 2-gang switch (which is just two switches mounted on one plate.
A one way switch turns a light on and off. You have a two-way switch e,g, at the top and bottom of the stairs, so that you can turn a light on and off from two places. If you want three places, you need an Intermediate Switch in the middle.
So to turn the hall and landing lights off, individually, from the hall and landing, you need a two-gang two-way switch. You can sometimes get 3-gang and even 4-gang switches, but more than that and you need gridswitches, which can be assembled to hold dozens. You may have seen them in shops and offices.
If you are carrying a stock of light switches e.g. in your van, you can use a 2-way switch as a 1-way, but you can't use a 1-way switch as a 2-way. So get plenty of 2-way switches.