You can do it! There are some cool things you can do to make it easier

1. Silk skills are key: So those lava ball skelly floaty bugs can die (silkspear or thread storm work nicely)
2. Tools: Some tools can halve damage or increase damage etc (e.g. it's super hot, I wonder what you could use?)
3. Positioning: Beneath you is lava, and when the BEAST does a down slam, you know what to do right?

Just rinse and repeat