After doing lots of run, i came to conclusion that even if people done so many runs and got explain, they keep dieing. Before starting run, set squad on free, so only 1 person focus on the axes at the toad boss (make sure that one knows what to do).
First boss:Needs 2 people do dig the the columns on side in same time to activate the boss. This is an easy boss, will have self buffs first time you hit it. A venomancer (werefox) is needed to purge or an archer with debuff bow.
Second boss: To activate the second, you will need to kill the mobs. This boss is not that hard but needs a bit of attention from party.
First of all when he gonna say

, some blue circles gonna appear on the ground. People needs to move away from them. As well, he will say

which gonna spawn few mobs, but careful cause they gonna freeze and seal you, and if you don't get purify or use faith in time, you gonna get killed by mob, in case mob wasn't killed.
After you kill it, to move forward, you have to walk a bit into the hallway like in the pic bellow:

A fire ball gonna come after that and don't rush into it cause it will kill you.
Third boss: This is a hard boss and lots of people do mistakes on it.
First i have seen it , people rushing into the room and dieing to mobs. If you can't tank them, please do not rush and avoid an useless death.

They aren't hard but they can kill.
After the mobs got all killed, the female in party will receive a kiss icon

. That one will activate the boss. Again, people rushing in getting the boss, without checking if everyone is ready, getting people killed as well. If you don't have a female character in squad, just kill one of the frog statue on the side and boss gonna be activated.
This boss is tricky but not hard if you do it right. First of all, the barb needs to spam "Fleshream > Alacity of the beast >flesh ream > Devour > surf inpact" from begining. Meantime, everyone needs to stay behind the boss.
Pay attention to this boss. He will gonna send an axes from time to time. Let 1 person do the axes.
The axes should look like this in your inventory (the one who is picking them):

Also when you see the boss having a blue shield, stop attacking till it's off because the boss just gonna regenerate his HP.
And one last thing, something so small that very few people pay attention to it. Beside the axes and shield, the boss will random stun and a psychic skill attack like this:

.
IF you don't use faith or spark to get rid of it (that if you don't have a cleric in squad to purify), in like 2-3 seconds you will be dead.
P.S.: lately seen this bug happen with axes. If you don't pick fast enough first one, it bugs and axes disappear. Now to get them back, whole squad has to DD till they get fixed. Should be fixed after 2-3 axes spawns. If this doesn't work then reset the boss.
Fourth boss:This boss got 3 action he is gonna use, so pay attention to your screen:
1. when you will see boss saying:

Means: barb can stay on the boss, but rest or the squad has to SPLIT away from boss and each other. Who stay close will get 1 shot.
2. when you will see boss saying:

Means: everyone needs to get closer to the boss, otherwise gets 1 shot.
3. after one of those 2 actions, boss gonna say:

Meaning, the boss gonna regenerate HP and needs to be disturbed. If you got a sin, he will have to use "Knife throw" and if you don't got a sin with you, barb has to use "Alacrity of the beast" .
Fifth boss (and last one):This boss is very annoying if you got high ping. Make sure you waste 3 spark before attacking because when he starts sending you chi, you will die instant and wonder why

.
For this one, you have to pay attention to your spark. He will send everyone in the squad chi for 3 spark.
When you will see the red text in your chat box:

After 2-3 sec max, boss gonna give everyone chi for 3 spark. Use it instantly or get 1 shot.
As well, he will push people back. Careful where you standing, so you don't end up into the flames.

I seen lots of people dieing to them and they didn't know why.
When the boss will have low HP, he goes rampage. Again, people don't pay attention to it. If you got a slow squad, you need to be careful, but if is a high DD squad there is no need to worry about.
Even so , the boss will self buff with aps and strength.

If you don't have a venomancer (werefox) to purge it, run around for few sec but also pay attention to your spark.
And that is Flowsilver Palace instance. Beside the frog boss, all other bosses self buffs when you first hit them.
I hope this will help those who didn't understood it. And last thing, don't try play the aggro hero in there. You can get your squad members killed or don't get a boss done.
Good luck to everyone
Rewards after full run:24 Flowsilver Coin
13 Perfect Element