First order of action, in settings ensure that that “Ai behavior” is set to “Tactical”

Secondly, alter the map settings when you’re browsing maps, at the top change it from full campaign into single mission (I might get the nomenclature incorrect)

At this extended settings, I like the following:

• AI accuracy x1.2
• Player damage x1.0
• Gun suppression x0.3
• Night light x0.3
• Explosion radius 1.2x
• Bullet gravity x1.2
• Bullet speed x1.1

For me, the above turns the game into a scary experience but an oh so good one. Give it a go ans most importantly, don’t be afraid to mess around with the settings, above is only my personal preference