@Rebecca2557
Do NOT give positive reviews when they are not deserved. Yes, both Hosts and guests can ask Airbnb to remove a review they have written. This means that you as a Host can remove a 5-star review you have written if you think it isn't a true reflection of the experience with the guest. This sometimes happen when a Host is too eager to write a 5-star review, only to find damage at the listing after they post it.
Better to write an honest review of the guest. This allows other Hosts to be aware of the guest issues. Would you want another Host to only give glowing reviews even if they are not deserved? You might base whether you accept a booking or not on that other Hosts review, only to find out this was actually a problematic guest.