Gendan, you can take your turn now since you are up next after Val. As for the Lecturn, you need to roll Athletics or Acrobatics. DC10 to cross but will cost 5ft extra movement, DC16 to cross without extra movement. Failure will not allow you to cross it and you will cost you 5ft movement. 

Because the stage is 5ft higher itself and it is not a slope, you will need Athletics or Acrobatics to get on the stage from anywhere except 6I (The rest of the room was segmented for mechanical purposes as the room is a slope. The stage is like a 5ft tall platform so you can't walk on to it normally without stairs). Because of this, trying to cross the lectern from 6M and 6N will call for a more difficult Athletics or Acrobatics roll.

You may take your  turn.

(What the hell, let's go for it!) Feeling the power after leaping the chair and goring the previous goblin, Gendan decides she's practically invincible (and quite the athlete). She bounds onto the stage, over the lectern and behind the curtain to O2. Seeing a goblin right next to her, she swings her shortsword at the goblin in P2.

Athletics: 21 Attack: 6 Damage: 4

(Lulz, looks like she probably made it there, but was too winded to put anything into the attack.)

Gendan takes off and in an impressive feat of athletics, jumps on to the stage and hurdles over the lectern in one swift movement. She stops at 3M (Out of movement).

You still have an unused action.

Gendan will Ready an attack if any goblin comes out of the curtain within reach.

Longsword Attack: 25 Damage: 9

The fearsome warrior readies her blade to behead any goblin that dare step within her reach.

Val and Folki, state your turn.

Val opens his eyes and coughs. He touches his chest, were blood is still pouring from it, the potion had just closed the most deeper part of the cut.

"Thanks Elsara. I really appreciate it. I am not ready to join the Mother's Final Embrance" he says to her with a faint smile. " Go and help the others.. I will be fine... " he tries to stand but then he sees the goblin that cut him down ready to attack Elsara and himself again. "Watch out!" He rolls and grab his scimitar, trying to cut the goblin while standing in one of his knees. Then he stands and tries to parry any attack.

As he leans against the chair Folki sees the new arrivals come in through the door at the back, cutting down Valwarin as they enter before they themselves are vanquished. He feels his anger grow and burn inside him. With a guttural roar he turns and launches himself up off the chair (enters rage!). He climbs high in the air before diving, the talons on his feet cutting great tears in the curtain through which he passes (9H to 2O 35ft). Using his weight as he plummets, he cleaves down with his handaxe at the goblin behind the curtain and then follows with a brutal hack at its upper leg.

(If he kills the goblin with initial attack, he will use his momentum to move forward to 2P and use the 2nd attack on the other goblin)

Attack: 25 Damage: 10

Attack: 17 Damage: 7

Val, Goblin13, the one that put you down, is still alive and still in melee range. Moving out of his reach will trigger AoO. Are you sure you wish to move to M18?

Folki, moving to O2 will take 50ft. In case of diagonal movement, first diagonal move is 5ft, next is 10ft then 5 and then 10.
Folki moves forward and tears through the curtain. Goblin5 gets an axe buried into his head and dies. Goblin6 says, "Rory? Rory? RORY!?" She begins crying and speaking in goblin while shaking the dead body.

 Val, confirm your action.

Val's prone state make his swings ineffective. The attack misses. Val, being prone makes you have disadvantage. Also putting it out there, standing up will cause AoO.

Goblin6 looks up at Folki with tears running down her face. She screams out in common, "YOU KILLED HIM! HE DID NOTHING TO YOU BESIDES TRYING TO DEFEND HIMSELF AND HIS FRIENDS AND YOU KILLED HIM! DIE!" The goblin moves to 2P and strikes Folki with her scimitar. Hit: 20 Dmg: 6
With her blurred vision, she ends up slicing the air in front of Folki than the bird himself.

Gym and Skiirod are up

Skriiod glares at Goblin13 for soiling his scales and armour in blood, he growls and swings down at G13. 

Attact on G13 Attack: 14 Damage: 11

"Woah!" The goblin says as he avoids the dragon's blade. He retaliates by attacking the prone druid. Hit:17 (Adv:19) Dmg: 7
The blade runs along the back of Val's neck and he faints again.

Elsara, Val, Gendan and Folki.

[OOC] Gym got missed over. Or rather, you called for his action then moved on without getting it.

From his spot in J18, Gym is in a perfect position to help deal with Goblin 13. He'd like to help Val but removing the goblin threat nearby is a priority plus he's exhausted his spells. Helping Val will take a potion or good old fashioned elbow grease. As an aside note, all the goblin screaming is really starting to get to Gymgiel's head, its... troublesome.. Attack: 6 Damage: 7

Oh, you're right thanks for the reminder.

Gym get advantage on his attack because G13 is pincered Hit:11

Narrating your turn as having taken place after Goblin13's because the end result is mechanically same in this case.

Gym sees the goblin raising  his scimitar to put Val down and rushes to his prone friend's aid. He is too late however and Val falls to the ground. Skiirod sees the cleric approach from behind and swivels out of the way. The goblin is caught off-guard by the sudden appearance of the cleric whose charge was hidden from his view due to the massive dragonborn standing in front of him. Gym uses his momentum to deliver a powerful blow to the Goblin's chest. He stops himself at 18J. The goblin coughs up blood and falls to one knew. He shakes his head and gets back on his feet.

Gendan, Val, Folki, Elsara. State your turn.

Valwarin, trying to catchs his breath attacks the goblin once again. His best bet to survive this was killing the creature.

Edit2: Death ST 20

Val, you can't attack. G13 put you down on his turn.

Regardless of what the narrative says, mechanically what happened was...
You went down, Elsara healed you with your own potion for 4. You are prone and attacked G13. Missed. Gym attacked G13 for 5 damage. G13 still stands. Skiirod attacks G13. Misses. G13 attacks you for 8 (Advantage due to prone) you faint. Roll Death Save.

Right cool, but now my previous question turns more important. Why does the goblin has an AoO for me standing up? Standing and moving will provoke it for the movement away withou using disengage, but just stand shouldn't. I changed my action of standing because you said that will provoke an AoO, if we misunderstood each other and just standing does not provoke an AoO then Val will stand in his first round, so the G13 hasn't advantage, so he is still up!

To answer your question, just standing up will trigger AoO. This is to make recovering from unconsciousness/ getting brought back to life more punishing. You can argue being prone is punishing enough but ranged attacks have disadvantage on prone targets so being prone has some benefits. Though the AoO that is triggered will not have advantage.

[OOC] RAW standing from prone does not cause AoO. Only moving out of reach does. EDIT: Not trying to look argumentative, I didn't hit refresh fast enough and you got your post in before me.