I suppose it's still their turn since we got ambushed and we had surprise. If that's not the case then..

After avoiding both arrows Arethal takes his battleaxe and his shield and runs to the goblins mumbling "You filth, how dare you..." and when in range he swings his axe aiming at one of the goblin's head

Attack: 17 / (if) hits for 6 damage

If I need a perception check: 19

Hearing the sound of arrows thud into the ground behind him, Thormund spins on the spot, holding his spear horizontally before him. He moves towards the direction the arrows came from, trying to perceive the archers hidden by the night.

Perception - 22

OOC - If the roll isn't Thormund's action, he will also ready himself to dodge the next barrage.

Borak

OOC: Do we see any enemies? How far away are they?

(are the monsters at least still unaware of Naadar? If so, and he can see where the arrows came from, he will try to sneak around and flank them.)

(if not, and a perception check is needed, he will do that instead before attempting to flank them.

(And if he was spotted, but sees them, he will call out in goblin for them to surrender while they still had a chance.)

Did Kathleen notice the arrows being shot? If so, she will return fire on monster 3 during her turn. Hit:26 Dmg:10

COC: sorry, guys, for providing insufficient context, my mistake

Arrows whispered near you without causing any harm and everyone noticed that there are three goblins sitting in the trees, one of them just blew the horn before striking you.

You start to hear a brutal roar coming from the cave as someone is going to come out of it.

Kathleen hit one of the goblins right in his head, pinning him on the tree. (he's dead)

 If I can't reach them then i'll throw a Javelin instead. If I could use my old roll (since it's the same bonus) that'd be great. Otherwhise 9

Javelin damage: 9

Also after throwing the javelin Arethal will back up a bit trying to hide from whatever is coming from the cave

Stealth: 7

I see. In which case, as I haven't taken a proper action yet. 

[In Goblin]"You should surrender while you still have a proper chaaance~ Foolish goblins." Nadaar says, eyeing and hitting an undamaged goblin with the most Vicious Mockery.

Wis. Save DC: 13 or suffer 2 psychic damage and disadvantage on next attack. 

Then in common he says to Borak after having heard the roar, "Well my friend. Let's show these goblins what for!"

Bonus Action: Bardic Inspiration[d6] to Borak. Lasts for 10 minutes and can be added to any roll but damage.

Borak

Borak throws a handaxe at one the Goblin then turns towards the cave entrance his battleaxe ready waiting for whatever leaves the cave.

Attack: 11

Damage: 4

Arethal launches a Javelin into one of the two remaining goblins sitting in the trees, but misses.

Nadaar casts Vicious Mockery on the same Goblin, he tries to resist it (Wis save 3), but fails. Goblin receives (4 dmg)  and falls from the tree (2 dmg), heavily injured.

Barack throws an axe at the last Goblin that was on the tree and smashes him in half with blood and guts splatters everywhere.

On his last breath felt Goblin tries to hit Thormund with a disadvantage Shortbow Attack: 10 Shortbow Attack: 10, he again misses, when he cries in common "Pesky bastards!" and dies.

Roars from the cave turned out to be three fast-moving wolves followed by two hobgoblins and one goblin that looked to you familiar he yelled: "These ones!" he pointed out at adventurers to the nearest hobgoblin.

30 ft between party and wolves, 50 ft between party and hobgoblins with a goblin.

Player's turn.

Kathleen moves back 30ft to increase the distance between her and the wolves. She then fires an arrow at one of the wolves. Hit: 25 Dmg: 11

Arethal highers his shield and yells to his companions "Take care of those on the tree, i'll hold ground". Then he rushes to the wolves and attacks one of them with his greataxe. "Someone please keep an eye on me and don't let me die!"

Roll: 21 
Damage: 8

Borak

Borak also rushes towards the wolves barely reaching them. He takes a swing with his battleaxe towards the head of the nearest one.

Attack: 19

Damage: 12

"[goblin] I warned you~" 

Nadaar grin turns into a scowl seeing the new arrivals. 

"Well ahead of you, my friend! And come now Kathleen! You can do better than that. There not even drakes!"

Bonus Action: Bardic Inspiration[d6] to Kathleen. Lasts for 10 minutes and can be added to any roll but damage.

"[goblin]That's right, hobo-goblin! Yes. You on the right! Your pets won't be enough! And -you- will be next!" He says, delivering another Vicious Mockery.

 Wis. Save DC: 13 or suffer 4 psychic damage and disadvantage on next attack. 

Borak

"You can run coward. But ya cannot hide." Borak shouts towards the goblin. "Surrender now and we'll grant you a merciful death."

Thormund turns and approaches the wolves, spear held ahead of him, pointing towards them. When he is close enough he brings the tip of the spear around in a wide slashing movement towards the nearest wolf. Utilising the momentum generated by the sweep of the spear, Thormund puts his body into a spin, following up his attack by whipping an outstretched leg towards a wolf.

Spear Attack - Attack: 19 Damage: 4

Leg Attack (bonus) - Attack: 7 Damage: 5

------- Players turn

Kathleen shoots an arrow into the wolf, but barely misses and the wolf took his way right to her, striding at full speed (60ft), roaring and chattering his teeth.

Arethal landing a heavy strike (9 dmg) on the closest wolf, but he seems to withstand, blood dripping down his skin.

Borak finishes that wolf off with just a perfect strike.

Nadaar perform another Vicious Mockery, Goblin (Wis Save 11) takes 4 damage and screams "You will pay for this! You will die!".

Thormund's spear hit last remaining closes wolf into his skull, followed by a sidekick that breaks his neck.

------- Monsters turn

Hobgoblins start to attack the closest target with longbows to bring it down as fast as possible.

Hobgoblin 1 attack Thormund longbow attack:  7 dmg: 5, but miss miserably.

Hobgoblin 2 attack Thormund longbow attack:  17 dmg: 5.

The Goblin who was bullied recently run closer to the cave and started screaming "Big Brother!! Kill Them. KILL ALL OF THEM!".

He tries to attack Thormund with disadvantage shortbow attack: 17  shortbow attack: 21 dmg: 5 and actually flourish in that.

Thormund stays with 1 hp.

A crazy growl spitted out of the cave followed by a speech "Who dares to kill my little brothers? I will kill you, I will eat you!".

Huge and angry ogre showed up from the cave, moving right to the adventurers, two hobgoblins flanking on his sides switching to longswords and shields "Pack tactics!" - yelled one of them.

(Alright. Which one of you chose nightmare difficulty?!)

"Oh that's just not fair." 

Nadaar comments, his once proud grin fading fast in the face of the ogre. Mustering his resolve, the dragonborn looks to Thormund first and says something in draconic.

"Endure!"

Bonus Action: Healing Word for 7 on Thormund.

With that out of the way, Nadaar looks to the Ogre, puffs out his chest, and then imperiously points at the the hobgoblins that didn't speak.

"It was him! The twitchy one! He use bad magic on everybody! Make'em fight. He want you hurt yourself punishing wrong people!"

Deception: 19.

(And if the check above isn't consider a full action..)

Nadaar narrows his eyes at the one he pointed out, unleashing another Vicious Mockery (for 1) in hopes of getting the hobgoblin to flinch in pain.

"Isn't that right... Twitchy!"