It's not easy because the champions league itself isn't all that friendly especially to new teams and I say this cause of the experience I have seen from most teams like Leipzig, Newcastle, and some others and all have failed to make any positive growth and that's why I don't feel any positive achievement will be made to their champions league campaign, but although am not sure for their Laliga journey but the champions league am sure that they will be knocked out.
Lije other breakout teams, Girona might find it very hard to cope with the intensity of the Champions league. It's not the Spanish league where they were familiar with all the teams they went up against. All the elite teams play in the Champions league and Girona will have much more on their plates. It's not just girona, but teams that arw prolific in their domestic league don't usually do well in UCL. See the likes or Salzburg or Newcastle as you have mentioned. I'd like to think that teams like that mainly consider their UCL qualification as an achievement and anything after that — getting past group phase, knockout stages, eyc as a bonus. Not to mentioned thru have sold some of their best players.