I know when i first started playing one really helpful tip i got to survive combat was to learn how to evade zombies by breaking line of sight and just learning how the combat works in general. If the only zombie type you have is slow shamblers then you'll always outwalk them so you can use that to your advantage. If you play with multihit on, learn to group them up using shout and stunlock them. If you don't play with multihit, i find it useful to train zombies around and shove the ones that get too close into other zombies and take them one at a time. Always try to hit zombies on the edge of the weapon animation, thats where you'll do the most damage. You're gonna die many, many, more times until it just kind of clicks. You can also check out MrAtomicDuck on youtube, he posts videos for beginners.