Welcome to KF2. I quit PD2 after 980hrs into it. Only things I miss is the soundtrack by Simon lol. Anyways into the brief things about KF2 I learned when I started KF2. KF2 is more team oriented than PD2. There are a lot of Zeds and if you were to correlate them with PD2 enemies, I would class Crawlers as Cloakers as they always fck things up. Sirens are Tazers as in Sirens shout is basically a life sucking vampire. Having 2+ on higher level is absolute nightmare so kill them on sight just like Tazers. Fleshpound (short FP) and Scarke (short SC) are the big zeds corresponding to dozers. Unlike the dozers these 2 zeds are nightmare to deal with if you don't know how to do it. FP takes double the damage from explosive and SC takes half the damage from explosives. The devs of KF2 wants the classes to be specialist. This way one classes shortfall is others classes perfection. I would advice you to search in-dept guides for each class to learn their potentials. This game has class/gun specific functions called Stun, Stumble and Knockdown. Stun is when the zeds stand still for few seconds. Stumble is when the zed flinches or move a few step back and knockdown is when they face plant to the floor. If you get a medic gun and shoot any zeds leg, they will stumble. This allows you to run away aka Kite the zeds. Each person has a 15 weight capacity exception is support class with +5 weight. Although I rather use the off perk which gives 10% damage. Some of the gun/weapons have alt fire or select fire. I recommend going into the controls and checking out the key binds. The default is right click ADS toggle. You can change it to right click ADS Hold to get the FPS style ADSing. Grenades do not pass Sirens that are shouting unless you have the demolition perk that allows it. Hans red shield = life sucking part so never waste your bullet during this moment and just let him heal by sucking you. Medic alt fire shoots darts that heals your teammate.