Don't use TIP120, that has a dual transistor output, you just want a single transistor to minimize the voltage across the button when the transistor is turned on.
1. Does MOSFETS exist in PNP and NPN to or is it only one type ?
2. Do you activate and use MOSFETS the same as BJT?
3. Is TIP120 a BJT ?
4. Witch MOSFETS do you recommend for me?
MOSFET uses voltage levels to turn on and off, very little input current, like 1microAmp. Outputs can be found with very low Rds (Resistance from drain to source) making them look very much like a mechanical switch.Power dissipated in the device is then related to current flow, P = I*I*R, so for high current, low Rds is very beneficial.1A*1A*.010 ohm = .01W.Bipolar Junction Transistor (BJT, NPN type and PNP type) need current into the base to let current flow from collector to emitter, with a more or less fixed voltage across C to E (Vce) of 0.5 to 0.7V.Since Vce doesn't change, power dissipated by the device can be high. P=I*V, so 1A*.5ohm = 0.5W. Big difference.In this application tho, where the current flow is low, but the voltages are also low, the low Rds of the MOSFETs makes more sense to use so the voltage swings can look more like the switch contacts you are duplicating.
Is JFET, FET and MOSFET the same but just different names ?
No.You need to look for a logic level FET. This is the second time you have been told this by me.