You evaluated the position correctly that is a good thing. When the opening ends, which you handled in this case well, the middle game starts. In this phase of the game you should make a plan. There are many types of positions with specific plans but obviously one can not learn them all. Instead of that you can learn strategic patterns just like the tactic patterns such as double attack or pin. But these strategic patterns are not so straitforward and you can not calculate them to the end like the tactic ones. You can learn these strategic ideas from books or videos or with the help of a coach.
One universal plan is to attack the opponents king to deliver a mate. How do you do that? You bring your pieces to the enemy king and with your pawns you eliminate the opponets pawns which are defending his king.
I tend to get lost in the middle game when something similar happens in person to games. If I am evaluating correctly: We have equal material, I have castled, linked rooks, and maybe a slightly better position. Theoretically what should I be looking to do next? What questions should I be asking myself? How do I develop a plan for the middle game? I am not looking for specific advice regarding this exact game..more general...Thanks in advance.