What if when i choose friendly unit with baited hook my baited hpok get destroyed

Yes — the ability still resolves in full. Once you've activated Baited Hook and paid the cost (including exhausting it), the ability is its own object on the chain; killing the Gear afterward doesn't cancel it (Rule 377.3, FAQ #5169).

So you still kill the chosen friendly unit, still look at the top 5, and can still play a unit with Might up to 1 more than the killed unit — nothing in Baited Hook's text references "my" or "here," so there's no dependency on the Gear surviving. Note the exhaustion cost was already paid, so you don't get the Gear back untapped or anything; the kill instruction is attributed to the ability, not to the destroyed Gear (Rule 428.5.b).

The only thing that would blank the ability is losing the unit target — if that unit leaves the board before resolution, its Might becomes null and you can't play anything from the 5 (Rule 359.3.e.12).