Depending on how much you pull from Troubles In Otari (and if you started with the Beginner Box), you will find the party is over levelled for the content unless you use the slow XP track. This will make some of the encounters trivial and some of the more difficult encounters average. I’ve been running it for almost a year now and the party has just reached the fourth floor and had a fair bit of trouble with one of the significant encounters there. They’re about 2/3 of the way to level 5 and could barely scratch the enemy, though they came up with an ingenious plan to pit two creatures against each other. Even then, it was still a difficult fight. Had we been using the normal XP track, they’d likely have been level 6 for encounters that are tuned for level 4.

Some more advice would be to flesh out the town NPCs a bit more (the expanded PDF helps with this). It gives the party more reasons to go back to Otari, can help break up the dungeon crawl, and allows you as the GM to raise the stakes by having those NPCs impacted by certain events.

As for PF2E in general, the mechanics work well. Try to emphasise to your players that standing still and attacking three times is going to make them a sad panda. Encourage them use of skills like demoralise, feint, and combat manoeuvres like trip and grapple. Stacking status and circumstance bonuses/penalties will make difficult fights a lot easier due to unbounded accuracy. PF2E is heavily focused on party composition and tactics rather than min/maxed individual efforts.