He was a strong foe. Powerful enemies will telegraph their attacks, rearing back to strike or summoning powerful magic. This shows they are about deal a lot of damage. It is good to learn their telegraph, so you can avoid the damage before it hits you.
Here is a reward that should help you on your journey.
Everyone has different problems when they face enemies. To some people, enemies have high health. To others, some monsters deal lots of damage. Remember what you are strong at. Learn what you are weak at. It is good to review your equipment often, as you can change it to improve your weaknesses.
Most bosses focus on a single type of damage. It is good to review and change your equipment if you have trouble against a boss. Gear with powerful elemental resistance is valuable to keep. You can equip it later for dangerous bosses.
I won't always be around. It is good to talk to the others, as they will often need your help. They will offer rewards in exchange for your help with quests.
You can also buy and sell items from some NPCs. It is good to check their items after quests. Some even offer old gems from quest rewards, or new gems you haven't seen before.