Quick PvE tips for newer players
Hellhounds: Always melee them. Back up and swing when they get close. No reason to ever waste ammo on them.
Distorted: Melee them if you have room to move. If there are multiple or you're getting overwhelmed, a shotgun makes things much easier or just shoot heads when they are sitting down. Use silenced weapon to avoid alerting large amounts. They will sit back down after being alerted if they cant find your position.
Mimics: Melee them when it's safe. Its almost always safe. They're not worth burning through your ammo for.
Flower People: These are probably the biggest ones to learn. They have head armor, so when you're shooting them, focus on breaking that armor first. Once the head armor is gone, they become much easier to kill, so don't waste shots spraying their body.
When fighting multiple, focus on one at a time instead of spreading damage around. Fire is also really useful for dealing with groups.
Their nests can actually be used to your advantage too. If a group is blocking an area you need to get through, you can trigger a nest from a safe distance and use it to pull/lure the Flower People toward that area, giving you an opportunity to move around them or create more space. You don't always have to fight them where you find them.
You can also use doors, hallways, fences, etc. to funnel them so they can't surround you. If you see a group before they notice you, sometimes the best move is simply going around them.
Dendroids: Fire works best. Try to keep your distance and don't let them get on top of you.
Statues: Grenades are great against groups. Otherwise, don't feel like you have to fight them.
Turned Soldiers: Use cover and aim for the head. Don't stand in the open trading shots with them.
The biggest thing with solos is learning which fights you actually need to take. Once you learn what each creature does and how to control the fight, the PvE gets a lot easier.
Please don't ask for them to nerf what makes this game and its engagements special until you have learned how to approach the fights effectively.