Breaking open the center is best when your opponent doesn’t develop much and just pushes pawns. You should do it when your pieces are developed, but you can still do it, but I suggest to prepare a bit. Prepare the rooks, knights, bishops, the queen up a couple or just one square and make sure you push your c pawn also so that you have enough power to break through. For the I don’t know what to do part, you don’t need to predict much in the opening(except an opening trap) because no one has enough power to attack and if they do, you will be able to defend, but just look at all the squares and draw arrows in your head( or in computer) to make sure you don’t blunder and this will help with that. For midgame, you need to predict so check for your opponents side on what they want to do and find ways to counter or if it is not much of a problem just improve your pieces. You will learn more online and through experience so I will not cover everything.
At my level this would transition into an endgame. In that scenario, a good idea is to refrain from trading in such a way to leave him with two knights and you have a bishop and a knight. The two knights will just have better prospects as they can coordinate better than a bishop and a knight.
But this is a 500 game. All you have to do, is just trying to not give away free pieces. That whole game, you made moves, and blundered pawns, but your opponent didn't see them, so you capitalized on it. I would work to stop making those types of mistakes in the openings where you are just giving away pieces. You opponent could have forked your bishop and knight in the opening... Play stronger players. Either at a local chess club, or by playing unrated games where the pool is players is a lot stronger than you are. then you will be punished for your mistakes and stop doing them. That's how I improved.
You opponent is just playing whatever openings. Sometimes it works for him, sometimes it doesn't. He is doing it because he doesn't know any openings probably and just picked that. There is no sure fire way to combat this type of advance in the center because when he is pushing more pawns then you are in the center it will be hard to make a breakthrough because you have no pawn majority's because he just simply advanced more pawns than you did and there probably isn't breaks. What to look for is weak squares created by his pawn moves. Once a pawn moves, the squares left behind are undefended, so your job is to look at those squares and see if you can get more attackers then he has defenders on those points. But in that opening it looked like you couldn't do anything if you both where about 1500 my rating, it would have ended up going into an endgame, and like I said a good rule of thumb with these openings is to not allow a two Knight to your bishop and knight minor piece imbalance, because most likely he will be able to create more threats for you to parry thus you burn more time on the clock thus you lose with time. John B had said, "Knights are better at blitz time controls." So, play longer time controls to avoid stuff like that. Or you don't think about what he is doing and bam he gains two pawns for free because your pawns where undefended and he attacked them with his knights.
It doesn't matter though. What matters is that you learn by being punished by strong players and fix your mistakes. playing people sub 500, is hard, even 800 is hard because they will make mistakes and your mistakes won't be punished, which is why it's so important to go over your games with a stronger player after you play your games so they can tell you your mistakes so you can drill them in and not make the same mistakes again.
don't panic. I used to just resign against pawn-pushers because I got in the habit of losing. I'm still a very low-rated player (probably always will be) but I realised that if you wait long enough, a pawn-pusher will finally leave something vulnerable, and their whole system will fall apart. Develop your pieces, preferably without losing any. If you have to sacrifice a minor piece to break open the pawn chain, or if you "accidentally sacrifice" one, you won't automatically lose, because you'll have better-developed pieces than your opponent. Better, if you get a chance to trade off a load of pawns, do so. Even if the trade leaves you a pawn down, the point is that you've developed your pieces, they haven't, so as soon as there's a hole in the pawn structure somewhere, you're ready to leap into action, they've got a row of statues at the back of the board looking ornamental...
I recently started playing & learning more seriously and am ~500/600 elo. So far I've been trying (and very slowly improving haha) to make sure I'm not blundering pieces, taking my time making moves and assessing threats, etc. I want to learn how to properly set myself up for a stronger midgame and started studying openings, specifically for this case I'm doing the trial on Chessly and learning the Vienna through that.
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In the game I linked I honestly started panicking a bit because I had no idea what my opponent was trying to do, leading to me taking too long to make moves and not playing confidently. As far as I have researched there isn't really any resources that explain what to do when your opponent hits you with the good ol' "move all my pawns to 6th line" opening. What is the best way to play in situations like this? What should I be trying to do, watching out for, keeping in mind when playing against people that just kinda "freestyle" in this manner?
Sorry if this is too amateur of a question but I am pretty amateur at the game still