In order to promote the game, I'm starting to publish videos which will show you features of the game and its stage of development.
So, #1 is about game physics.
In order to save yourself from the heavy enemy fire, you can grab any nearby items and use them as your shield or make a barricade out of them. The position of grabbed item is not fixed, you can hold and drop all items how you want.
For example, take two or three wheels, make a mini-tower out of them and put a garage door on it. Hide behind it, wait until enemy reload and shoot him.
Improvise and be fast, this is the only recommendation against enemies with guns.
You need to be extremely careful: 3-4 bullet hits and you're dead and there's no almighty health regeneration out for you. You need to find and drink Vermouth bottles to replenish your health.
If you see some place which seem impossible to reach, don't worry and look around.
For example, there might be some very heavy item is blocking the way. If you can't jump over it, make stairs out of something.
NB: Glass it's not an obstacle, you can break it. You can also break certain walls to find more secrets!