At this point in the story Atreus has gained Sonic Arrows so you can easily apply status effects to enemies. So you can change from Niflheim Enchantments to Vanaheim. The Vanaheim set does more damage then Niflheim so it is worth changing over eventually. However you might want to wait until you get Sigil Arrows since Sonic isn't a good status effect for doing damage.
Keeping that in mind I found 2 ways to efficiently and quickly defeat this story boss. Alva is the last of the easy story bosses. The next one Kratos fights is Vanadis/Freya and she is roughly the same difficulty level of one of the weaker Valkyries in the 2018 game.
![](https://s2.save4k.ru/pic/0rEqCtXQoqc/maxresdefault.jpg)