M M A
Yes why not
1. Make the sword you are using and armors have upgrades of more than 500 to 600+. The amulet and ring and also wings.. you can upgrade them also but I know it's much harder to collect magic stones than others but you must upgrade it as much as possible so your resistance to fire will increase.
2. When attacking the dragon, and all skills cooling down, you can jump->attack before the fire breath hits you. That way you can hit the dragon while still in the air and follow up with more attacks.
3. If you can unlock the allies knight of evelyn castle or knight of Norwand. You can use it to help attack the dragon while it's sitting down and you are dodging. That allies deals massive damage to the dragon if the timing of summon is perfect and will not be hit with fire breath.
I hope this helps you. But truthfully, there is no need to go to dark mode immediately because it's really hard if there is no unique weapon. All unique items can be acquired in inferno mode if you play over and over.