One thing in the beginning a single player game does not have to be perfectly balanced. As we have already explained it, let's move on. Some changes from the DnD rules are needed, otherwise the fight at low levels would be quite limited.
What? No way. D&D 5E rules at low levels offer a lot of variety: see Solasta for example. Most actual d&d play never gets beyond level 5 in the real world haha.