Question trigger event with update event not possible

Need some help here i am a beginner.

i have a bird on ground i want it to fly on trigger enter on collide, the problem is this bird needs an update function to keep flying and i cannot add update function with trigger event function, how to solve it ?
i tried translate relative to but its teleporting to a specific location.
i tried add force on rigidbody not working as well on all modes, either it teleports or moves little bit only.
it needs an update function to keep flying every frame.
thx...

 

No problem nobody answered my question, i solved my problem with a state machine, not a helpful community though
just saying...
thank you.