Things got better for a week

Hey again ! I’ve read a few things in this sub but I’m still a bit confused on some topics. Two weeks after pest control came, we didn’t see any roach for a whole week. Which was good. But now we’ve seen 3 in 4 days. Does it mean things are going back to bad or is it part of the process ? We have some Advion gel that we haven’t used in our appartement yet, just in the common areas of the building. Does it mean it’s time we put some gel in our place ? I’m really confused about why they’d be coming back. We’ve kept our good habits, we’re always cleaning and we never leave any food or water out. Also, we won’t be asking for pest control from our landlord. I won’t put my cats through that again. They put some gaz bomb thingy so we had to not be there for around 6 hours and it caused so much stress to my elderly cat which of course affected my other younger cat. So what do we do from now ? And is this normal ? Thank you in advance for taking the time to read this !