New Player Struggling (40 hours played)

I really really like this game so far. It has the expansiveness and excitement of two game types and I love the depth/content.

I've tried to orient myself as best as I can. Trying all the classes, certing abilities, working together with teammates, parking sundies strategically, hacking guns and terminals, rocketing vehicles, etc. I've watched tutorials on capturing, compensating for gun spray drift, weapon types, and more.

I'm getting absolutely wrecked. Constantly. I die incredibly quickly each time I spawn unless I just perma cloak on top of a mountain. Not like getting a kill every other life, but more like 1 every 10 lives.

For example:

Spawn at invis sundie, enemy max can somehow see me anyways, minigun shreds me in 1/2 of a second. Respawn, max is gone, sprint toward teammates in building, flying vehicle shreds me in 1/2 a second. Respawn, make it to the building, set a up a turret, jump in and starting hitting people peaking corners, get a few hits, BOOM headshot sniped through the turret somehow. Respawn infil sniper, make it to high ground, find protected spot on ridge, peak, find shots and devis, get a few hits, no kills, BAM backstabbed.

I have 0.3 K/D.

I know this is a classic beginner post, but I feel helpless. How can I even begin to improve at this game if it's like this?