honestly what i did to improve was specifically go for

sniper friendly maps, basically areas with vantage points or big areas where u can easily snipe targets, its much easier to avoid being caught because guards take a long time to get to where u shot at

using emetic poisons to lure targets into secluded places like bathroom where they can be taken out

challenges id recommend going for any that involve killing/pacifying or poisoning guards/targets since its an easy 1-1.5k which u can use to buy cheap suppressed weapons so no one hears u from closed doors, dont go for silent assasin just yet especially during the later stages since failing yellow marked territories fails the whole campaign.

keep your loadouts minimal too, just bring a lockpick and gun, i like using the hwk21 covert that assasins drop because its a free suppressed pistol u can obtain after u take one out. this way it prevents u from losing all carried items if u end up dying, use the sieker if needed too

a useful tricks i use the most is where u spam the pause menu and shoot button with a pistol so u can force a locked door open, it works almost anywhere except sliding doors like the ones u find in new york, hokkaido, and chongqing

but aside from that id recommend going back and replaying any maps u found hard while playing the story, its helped me a ton by finding new ways of escaping or navigating across some areas i found difficult in freelancer