For those with Nicola error I think someone and bryn have said that it's not using the latest translation patch. Latest translation patch on ULMF should fix that so visit there and give your thanks to the 1 did it.
Tips for those having hard time fighting
HIGH agi will make you able to do double attack on normal attack, most of girls below floor 30 have quite low HP so double attacking them will instant kill them.
There will be an equip that make the girl flinch on first turn - combined this with double exp item and you can have easier lv grinding.
Been playing with trials and errors here and there and here's what I did :
DAY 1 - GRIND up to the first mandrake - save - continue up to bear boss then go home from there - by doing so you should have equips with high agi.
DAY 2 - Go to lab make some strength potion and elixir incase you don't have equips that make your skill cost half - grind again from mandrake floor up to bear boss to find a succubus that is looking for her ONII-CHAN~ cuz she will drop an item that makes you able to equip 2 swords (AHEM!) - make sure to be on lv 30-40.
DAY 3 - Gave all my lv to Sophie so she will EAT ME.....cook a dish that can give 5000 SAN - start from bear boss get up to boss stage that is up on succubus boss.
DAY 4 - Gave the rest of my lv to scientist then gambling on buffs - start from succubus boss stage and go ALL THE WAY to top floor. Prepare elixirs cuz last boss can pack quite a....uhh.....HEAVY LOVING despite my lv is 90++
FOOD TIPS - Keep at least 4 snacks and 4 chocolates and sophie love lunch if you plan to go all the way to top floor from succubus boss floor. My playthrough was not smooth that few times I have to load back cuz I was out of SAN on floor 40++ and have to skip fights, was lucky to find snack on the way to top.
SPOILER - On top floor you can choose to go home instead of taking the gems and proceed to postgame clear, I got 2 achievements cards by clearing it fast. There will be option to pick who's ending you prefer too on top floor (I will just say this much, find out more yourself)
Some NPC you will fight in dungeon :
Girl looking for ONIICHAN~ - was on lv 40-50 so she's practically down using only normal attack, not that strong. Recommended to beat ASAP.
Eye patch mercenary - Can be quite problematic if your lv is below 40, will not kill you even if you die (unless you ask for it on her event)
Nun healing your SWORD(?) - Can paralyze you but she's pretty weak overall, nothing to be scared of
Random cat merchant - Is still challenging even on lv 30, will heal you when you lost.
Nicola - Beware for game error before fighting her, had same difficulty as fighting mercenary.
DEM thief - The only NPC fight makes me regret of fighting her....after Nicola crash that's it...Her attack often paralyze you and ONCE you do she will barrage you with 3-4 high damage attacks. Personally testing her on lv 30+/40+/50+ and lost horribly before I snapped and finished her on lv 70+