Did I have to see the first one in order to understand/enjoy this one??

No, you don't.

O freddled gruntbuggly Thy micturations are to me As plurdled gableblotchits On a lurgid bee

The movie begins with an Evil Dead style retelling of the events of the first movie, so no, you don't strictly have to see the first one.

But you'll enjoy it a heck of a lot more if you do.

Tesla was robbed!

You don't "have" to but you'll appreciate it a lot more if you do.

The second movie is far better and different in the way it is presented throughout and it includes them showing clearly what the background story is from the first movie so no you don't have to watch the first movie. Still if you do watch the first movie don't let it stop you from watching the second. They are quite different in my opinion in terms of overall quality. While I really liked the first movie and wanted to score it higher it just wasn't the automatic 10/10 the second movie was.

I watched it on Netflix without seeing the first and understood quite well... I don't think it relies on much from the first movie aside from Nazi Zombies and the main character.
It actually did kind of remind of Evil Dead 2 in comparison to The Evil Dead... you don't have to see the first Evil Dead because ED2 stands on it's own well enough, and only carries over a few details (Ash, Cabin, Insane Woods, Deadites, Book of the Dead).