Simple DnD Map Version 1 Feedback

Simple DnD Map Version 1

What went right?
My map's overall layout was fairly simple, there were not many turns or twist. I wanted the first map to be more linear and catered to being a tutorial level for the players. The first area (aside from the spawn area) is the Hall of Reeds. There were three weak skeleton enemies for the players to fight as a tutorial enemy. The playtesters had no problems defeating them. The boss was both right and wrong. It might have been a bit strong but at the same time, the players lasted a fairly good length of time. This could have been both the impact on the dice rolls and luck, however. The length of my map was also fairly good. The players got through it around 20 minutes. 

What went wrong?
The part that went wrong was that my map lacked squares, making it a bit more difficult to navigate and the combat didn't apply the range rule with the classes. The map was also more basic, it didn't give obstacles aside from enemies for the player to interact with. Also, I have never played DnD before so getting into DM-ing was rough at first. I didn't write a script to fall back on so the storytelling wasn't as smooth as I intended it to be. I didn't know we had to give similar stats to the enemies so the combat was wonky. I wasn't exactly sure how combat worked so I had to quickly learn and calculate the rolls and stats.

How might you improve your map next time?
The feedback I received from this playtest was extremely helpful. For future playtest and to improve my map I'll be adding grids so the players can use the range advantages of the ranger class as well as having the immersion of the map in terms of length. I'll do better with storytelling and definitely make sure to add stats to my enemies beforehand. Having a script on hand to fall to would be nice too.  

Were the challenges presented appropriate to the introductory/tutorial nature of the level?
I gave out challenges that I thought were appropriate for an introductory level. The first enemies that the players encounter were three skeletons each with a defense of 1 and attack of 2. They weren't extremely weak but not strong either. Though my weak dice rolls also made them a very easy challenge, most of the time I rolled numbers lower than 4 which made the enemies very pitiful. Regardless they served their purpose as fodder. However, the next enemy was a small boss with a defense of 3 and an attack of 3. It wasn't too difficult, the playtesters spent a fair amount of time in combat with this boss. However, at the end with the last standing player and the boss near death, I luckily rolled a 6 on the boss's attack turn and defeated the last remaining player. It was a very close fight and I felt it was fair. 

Was it obvious where players we supposed to go?
Yes, the layout was more on the linear side. There were only three main rooms and it's lined in a linear path. There are two other rooms that were meant for items (one for an armor piece and one for a weapon) but I later learned they were not necessary for this current version of a DnD map.  

How was the overall flow?
For a first map, things went pretty smoothly. Mainly it was thanks to a playtester who had DnD experience to explain things to me and the other playtester, both who have never played DnD. He was extremely help in explaining the enemies and how combat worked because those were the two parts me and the other playtester had trouble grasping. Things could have gone smoother if I had a solid script and enemy stats starting this campaign. But regardless, things went better than expected for a first run.