Dark drake in nightmare

I have a problem in the lvl 10.10 of nightmare: i don't have the dps for clean the level in the 5:30 (paying one soul for +30 sec) , because the dark drake is always flying and untargetable (i can hit it like 3-4 time every 15 sec... )
My sword is tier 10 and +70, and i'm close to kill the drake why the time end... but it cost one soul everytime so i don't want to ty it 50 times 😂
If someone can tell me a trick or tell me how yo get better sword ( my def is ok) .... the problem is the boss, i clean the third first zones in less than 2 min ! But after with more than 3 min i can't dps the boss and he is 10 or 15% hp when time runs out.

And my stuff, pls tell me if he's good or not, i farmed long hours for it!
Try to use skill when it flames down to you . Attacks are always welcome there. You can draw equipments in shop icon below your lobby screen. If possible try 100 souls draw. Again try upgrade your sword. Use dodge if needed.
Grade matters for improvements:
Normal (black)<magic (blue)<rare(yellow)<epic(green)<legendary(orange)<unique(red)
Try to use skill when it flames down to you . Attacks are always welcome there. You can draw equipme...
I didn't dropped more than a rare sword... and i try to use my spell every time he come flaming, but i only have two smells so... when i don't have i just roll behind it and 70% of the time i don't get the damages.
I prefer keep my souls for tier 15 equipement because it's the final equipement and i want a nice final stuff (i only have 600 souls for now, didn't used since my begining)
I'll upgrade more my sword as you said, but i don't like that because i'll change it soon for a tier 11 sword (when beating this drake and going to infernal zone, where i'll can dropp every tier 11 equipement ! )
I think i'm not really lucky on drops, i didn't get any legendary items, and no epic sword since tier 7 😭
I think i'm not really lucky on drops, i didn't get any legendary items, and no epic sword since tie...

You won't get anywhere if you don't make little sacrifices. The 1st problem is you said you won't buy in the shop because you are keeping all your souls for Tier 15 swords. 2nd Problem you said you don't like to upgrade your current sword because it will be replaced by tier 11 once you get to the next level. Then what other options can you do? Nothing...
The solution is to buy in the shop, preferably 100 souls purchase. There at random, you can get legendary or unique swords that fits perfectly for your level and have 4 skill sets like those swords in the picture. Dont get discouraged if you get nothing at first because like gambling you can be luckier next time you draw. You can replenish your souls again by gifts and daily raids and free 3 souls.
2nd solution is to upgrade your current sword. Use the gold that you have now cause you will get more gold farming from previous levels especially 9-10(recommended) over and over.
Tip: use save souls gradually and not spend all in one go. 200 today then next week again so you won't feel so much pain losing save souls. Or if you are impatient, buy souls in limited items tab. There are great deals for souls in there and is worth it.
When attacking the dragon use dodge to evade flames or jump/ do the overhead attack (with sword striking the ground) when the flames is about to reach you. You can do it by pressing jump then attack in quick succession. Its not easy but by practice, you can get used to it. Benefits - even when the dragon is in the air it can be hit by that strike. Damage is equal to or almost to power strike. It is a good option when skills are cooling down.
Do not hope too much for epic or legendary swords in drops cause they are rare now. If you want to be powerful by not spending souls in the shop then upgrade your sword. Sacrifice gold to save souls. Not worth it if you keep losing time and 1 soul just to finish a round. Goodluck.
Hi, thank you so much for your answers!
I think i'll upgrade my rare sword tier 10 for kill the dark drake
Then when tier 11-12 will be open i'll use my souls for it (100 if i get a nice stuff, 200 if i don't) then do it again for tier 13-14 and finally the rest for tier 15 😁
You said getting souls from gift, i don't understand how it work, three or four days before I got 30 souls but i don't know why ( there is a weekly gift?)
Can you please tell me what are the better stats to have on a sword? For now i try ro have strengh, vitality and attack speed. Bonus damage is good too but i prefer strengh
(On stats personnage i saw it was better)
And for the other items i try to have vitality, then strengh, and finally bonus armor and bonus HP
And I don't know what are the intelligence and the dexterity 😮

Finally did it !
Thank you both for you help and answers !