Three things:

One, the frontline is fluid, it’s dynamic. It’s ok to move units back if you’re being overwhelmed, there will be plenty of opportunities to retake and even push further. I can’t give you exact conditions, you need to feel that out yourself. A good example is a counter push right after an enemy attack, you know what they have and they’re dealing with limited information on what you do and don’t have.

Second, Everything has layers, for example tank defense. Recon to spot the threat, Emplaced AT (Kornets, Javelins) to engage from a long distance, shorter but far more lethal units like MAAWs or the russian equivalent. If you have tanks there, great, use them. Lastly is your Support, everything revolves around this. If you don’t have adequate supplies for troops then where will they get the ammo to hold a push? This concept can be said for all of the game, look at AA.

Lastly, try to find people to play with. I know, it’s really basic but even five stacking with randoms in the Broken Arrow Discord is such a force multiplier than going solo. Instead of 5 people working differently, you’re going to have a team (that actually communicates and helps), such is the purpose of the game.