Recommended mobile app or website to memorize openings? I'm looking to improve my game's opening. 
Just wondering if any of you could recommend an app or website dedicated for this?
Chess PGN Master and pgnmentor.com are how I study openings. Download one of the large PGN files on the opening you want to learn, open it up with the viewer and autoplay through games during your downtime. I tend to stick to the games of only the players I recognize so that I am not learning from 1300s (there are a ton of high-level games in each file). This is great for learning the common themes of an opening. You don't have to understand every move but sometimes I will pause it and try to work out a particular tactic.

To memorize specific lines, I make openings files in Chessbase built from the games of today's top players (I consider anything that a 2600+ FIDE has played and my computer doesn't immediately hate to be playable for me). I then play through them, forcing myself to remember the options available for each side in the position before I make the next move.

As others have mentioned, focusing on openings is not going to help you improve very much below maybe 2000 FIDE. However, the first method I described can be used to improve at any level-you can retrieve all of the games of a great player (I started with Capablanca) and watch their moves zip past. This in my opinion is the best way to learn pawn structures. Jeremy Silman has recommended this method (though not this specific configuration) many times in his chess.com articles.