What advice would you give to the real estate agent?

I do not recommend this real estate agency, firstly, they are always on the owner's side, they take a long time to resolve problems (months). In my case, they delivered a poorly written contract, which said they were supposed to deliver the apartment painted white, when they delivered it to me painted beige. I recommend reading the contract carefully and taking photos and videos before rent.

What advice would you give to the landlord?

Be careful that you don't want to return the full deposit. In our case, I wanted to keep half the deposit because we didn't deliver the apartment painted white, when it was delivered to us painted beige. And he's always looking for flaws to keep some money. In the end, we went to court against the owner for her lack of scruples.