You will not find a tutorial on how to make a complete game of that calibre, but you will find tutorials on specific features, sure.
multiplayer, third person shooting,
picking up guns, aiming, and health
What you mentioned might be a good start, that’s providing you’ve learnt the basics of the UE4 editor already; otherwise I’d focus on that first. YT is your friend here.
where i can get free content for that
Have a look at this list:
And check UE4 marketplace, lots of free goodies there!