What would you recommend?

I am new to chess. I have been watching a lot of chess masters play beginner to master speedruns. They will use a single open for black or white. I have tried many of those opens and noticed that a single open played by a master looks easy, especially when they are playing against low elo players. I have realized that a player at my level gets crushed if I don't adjust my open. Example, I have settle on the Italian for white and I can hold my own vs. most black 1...e5, 2...Nc6 defenses, but against Pirc or Slav, I have gotten crushed. I am now using the analysis board to see the recommended moves for white, after black plays something other than 1...e5.

Do you think I will be better off making the adjustments right away or would you recommend sticking to the first 3+ moves of the open I choose to play as white? Either way, I know I will have to keep using the analysis board to determine the best moves. 

The reason chess masters can do beginner to master speedruns with any opening is because the opening is the least meaningful part of chess. I'd definitely recommend learning tactical motifs and endgame theory as opposed to opening theory. My opening knowledge theoretically is massive, both in depth and breadth, but I never use 95% of it, but I know how to execute nasty middlegame ideas from essentially any position or at least how to trade down into an equal endgame.

Note that is illegal to use the analysis function (i.e., a chess engine) to calculate moves for a game in progress.

Chess Openings Resources for Beginners and Beyond…

https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond

Yes, I am aware of that. I use the analysis to review after I finish a game. I check to see how to play a situation that I wasn't sure what's the "best" move. There are key moments during the first ten moves that can make or break a game. Do you take or not take this piece? Do I move this piece or that piece? Sometime the answer changes based on the moves your opponent makes.

I do practice middle and end games, knowing their importance to finish off an opponent. I believe getting off to a good start puts me in a better position to play what I learn about the middle and end games.