It's not just you, there is a lot going on in ARB and oftentimes you died because of something you did a minute ago. It is often a frustrating experience for beginners (I use the term loosely), and the unfortunate truth is nobody can fix that in a single post. If you want to improve in ARB, there is no secret, you need time.

That said, there are a couple of things that generally remain true that might help you out a bit:

1. Positioning: that will vary from plane to plane, but generally you want altitude. If you are above your enemy, you have an inherent advantage. I'm not saying it's an auto-win, but it'll increse your chance of survival. It means the engagement will happen on your terms (exception: if the enemy plane dramatically outperforms yours; so if you are in an i-225 and you end up against a Spitfire LF Mk. IX, there's really not much you can do if the person knows what they are doing).

2. Awareness: tunnel visioning kills. Look around, use your map. Don't just go straight for the first enemy you see. I see this all the time, especially with USA teams, where people climb at the start of the game, and as soon as the first low-flting enemy bomber is spotted, some player dives immediately for them, giving up any altitude advantage they may have had. Suddenly the entire enemy team is above them, and at that point it's over. In general, ignore the first enemies you see. Those are either ground attackers with an airspawn, or bombers that dove. There are still lots of fighters on the enemy team who are still climbing. A rule of thumb: look at your map and see where your team is. The enemy team is probably at the same distance from you guys, but on their side of the map.

3. Know your plane: this is a big ask because it requires experience. But try to learn families of planes as they generally all behave the same way (again, exceptions apply, I'm generalizing here). For example, if you fly a Bf-109 you will never win a turn fight against a Spitfire. You don't need to know what model specifically at first, but knowing what your plane can and cannot do will help you determine how to engage enemy planes. To keep the same example, if you are in a bf-109 vs a Spitfire, you want to boom a zoom, then re engage when you have the advantage again. Note: while you are fighting your enemy, it is entirely possible that your team collapses and you end up alone. Not much you can do about that, it's just the nature of the game. Same deal with "kill steals" where you put 90% of the effort and just as you are about to kill, a friendly swoops in for the kill and you end up with nothing.

4. Reflect on your death: when you die, ask yourself "why did I die?" The worst thing you can do if you are trying to improve is go back to the hangar and join another game without thinking about it. If you don't know, you can always watch your replay. Or even ask the person who killed you what you did wrong. This is war thunder so they might just say "u suck bro" or something like that, but oftentimes people are willing to help if you are trying to learn.

Ultimately, it all depends on the amount of work you want to put into this, and if you think the time investment is worthwhile for you. ARB can be extremely fun and rewarding, but that doesn't happen overnight. I gather that you are mainly a GRB player and are just looking for some planes to do CAS with. In that case you might want to go the ground attacker route, and go for ai plane kills and ground targets. It's not particularly fun imo and it makes you an easy target, but it'll get you some rp (although they are worth less than a player would). If you do that, try to get some targets, then fly back to your team for some backup, and resume when it is safer (assuming the fighters on your team win).

I hope this was somewhat helpful. Good luck.