This is where I'm going to dump a ton of general advice that you'll be rewarded for internalizing.
Master your mechanics. You cannot exit the beginner stage of your journey until you are able to move and input your sequences cleanly. You will not learn how to make good decisions until your decisions are accurately reflected in-game and you are playing with full agency. In addition, absorbing concepts is challenging when you are constantly second guessing yourself or concentrating on your inputs. Your inputs must become second nature. If they are not, practice in training mode. It is tempting to just play the game but one hour of movement practice will do you better than 10 hours of unfocused PvP games.
Experience trumps all. At the end of the day, you WILL improve by playing the game more, as you slowly absorb the various concepts. Even if something makes no sense to you now, it will come with experience, and there are many things you won't be able to learn unless you experience them for yourself. Sometimes you need to see yourself make the mistakes in order to internalize the lesson. The golden rule is to make sure you're playing the game. If heeding the rest of this advice makes playing the game too boring for you, ignore it and have fun.
One step at a time. Each individual aspect of the game is a hurdle you can overcome, so focus on one thing at a time. Setting small, realistic goals to improve on will help you stay motivated and ensure you have takeaways from your games.
Watch replays. Unlike many other competitive games, 99% of the time, the best Gundam players in the world are doing things you can mimic perfectly. Inputting is simple, decision making is hard. Watching replays from strong players will give you a fast checkup on whether you're on the right track or not. Use videos as a reference for what moves to use and when. You can learn what range you should be playing at, and what your suit's general gameplan is.
The HUD will tell you how to play. There is a ton of info visible with the game HUD - enough context to greatly inform your decisions. If you're not sure what you should be doing, chances are you just need to look at the HUD. You/your partner's HP and Burst values. Your ammo status. The minimap. Your enemy's HP. Who is (and isn't) targeting you. Your team's HP values will tell you how risk averse you should be playing. The lock situation will inform you whether to defend or attack. If your strong moves are on cooldown, consider waiting. If you or your partner has burst, play around that. The list goes on.
You cannot reach a higher level without aiming for it. The next four points are more specific but all touch on an important key piece of advice: if you want to be a high level player, play like everyone else in the match is one. You will be tempted to lower your level for various reasons. Perhaps your partner is unable to keep up, perhaps your opponents are too weak. In either case, allowing desperation or complacency to affect your gameplay will ultimately decrease the amount of takeaway from your games.
As long as you're not getting hit, you're not losing. While this isn't always true, the important thing to learn is not to feel uncomfortable just because you haven't hit your opponent. If neither you nor your opponent are hitting each other, the situation is even. The game itself is very asymmetric. Wait until a more favorable opportunity presents itself, or work towards creating that opportunity. Resist the urge to force interactions unless they're in your favor. *NOTE* this is not the case when your partner needs help.
Do ONE suit's worth of work. No one is expected to pull more than a single person's worth of weight. Forcing yourself to break out of a 1v1 to go focus fire with your partner at the expense of leaving an enemy unmarked is a common mistake. Often times, your partner will be fine, and may be wishing you stayed focused on your target. Similarly, expecting to try and win 1v2's is unreasonable. Lastly, when playing matches with uneven player skill, you may feel you need to "carry" but...
Ignoring theory to get the quick W builds bad habits. When you are experienced, you'll recognize when you need to do what it takes to win, especially in tournament or serious matches. But when you're at the stage where you're still trying to internalize core concepts, abandoning theory because you can't trust your partner is stunting your growth.
Do not focus on what is out of your control. Gundam is a team game, and sometimes you'll lose games through no fault of your own. The important thing is not to be discouraged. Focus on what you're doing right, regardless of the WIN/LOSS result.
Have faith in cutting guidance. Sidesteps and other guidance cuts may not look like they're doing much, but are typically better at avoiding things than displacing yourself with normal movement like boost dashes. Most of the time the answer to "how do I avoid that?" is to step BD.
You shouldn't have been there in the first place. Gundam is a game where each player is taking a sequence of actions before they have to land and refill. If you get hit at the end of your sequence, the answer, the correction, is often happening much earlier. The most common example is losing to close ranged suits. There are lots of suits/matchups where you will have a very poor chance once you're close to the opponent, and the correct thing to do is not to let them get that close to begin with.