I wish there was a wiki for this game. I can't seem to figure out how to get past the magma level
Magma zone applies a Burn debuff to your turtle that increases stamina cost by +1 per dig, regardless of your digging power. This means every dig will cost at least 2 stamina, even at max Power. There are some accessories and footwear designed specifically to help with this zone (I won't spoil which ones in case you haven't discovered the blueprints yet), and they're quite important for progressing through the magma zone especially early on. Otherwise, increasing your stamina, stamina regeneration, or light radius can also make a difference.