So for example, you are walking somewhere and then at a certain point somebody appears and move a little and then disappear so something scary in a horror game, so my question is do you need to first make a full animation in maya and then import it in unreal engine and just let it animate?
An other example is if you are walking somewhere lets say a forrest and and there are many birds on the ground and if you approach them they just fly away and then dissapears, do you need to create a full animation in maya and then just import it in unreal engine? how does this work?
It always depends on how realistic/good it should look ^^ Theoretically you could move something with matinee + without a animation but then it has to be very fast to look good. But normally you create e.g a fly animation - then you place it - trigger it when the player gets near - destroy/hide the mesh
Assuming an NPC, you want to keep things as simple as possible, what is current on the UE4 road map is vertex or point cache data animation.
Once that feature is added how I would go about it would be to create the animation, in this case 3ds , and export the NPC as a static mesh containing the PCD, which FBX already supports it, and when imported into UE4 would contain parameters to turn on or off that animations in real time as well as to index where the playback should start.
See the Point cache data modifier in 3ds to see how it should work as imported.
With this set up it would be simple enough to hook to a trigger event, use some funky material magic, and would work as simple as turning on and off a light.
You can do that in your level bp. Just add a trigger - connect it with a e.g matinee sequence (so that he moves from A to B) + a play sound node - add a delay - add a destroy actor node
Now when the player touches the trigger the mesh will move e.g out from a wall the sound will be played and after that it deisappears.