When Geralf's Mindcrusher dies, its undying ability and Goldberry trigger twice.
Resolve the first Geralf's Mindcrusher trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
When Geralf's Mindcrusher enters the battlefield, it triggers, causing a player to mill five cards.
Resolve the second Geralf's Mindcrusher trigger, doing nothing.
Resolve the first Goldberry trigger, untapping it.
Holding priority, activate Goldberry's first ability by tapping it, moving the +1/+1 counter from Geralf's Mindcrusher onto Goldberry.
Resolve the second Goldberry trigger from step 2, untapping it.
Activate Goldberry's second ability by paying ({U} magic symbol) and tapping it, moving the +1/+1 counter from Goldberry onto Teysa, and causing you to draw a card.