Dreams often reflect our subconscious thoughts, feelings, and experiences. In your dream, several elements stand out that may provide insight into your current mindset.

1. Visiting an Ex: This could signify unresolved feelings or thoughts about the past. It may represent nostalgia, regret, or a desire for closure in that relationship.
2. Fire Alarm: Alarms often symbolize a warning or a call to attention. This might indicate that there are aspects of your life that you feel need urgent attention—perhaps related to your relationships or personal goals.
3. Mushroom Farm and Housing: The contrast between a mushroom farm and the need for housing could reflect your thoughts on priorities and societal issues. You may be grappling with feelings about what is important to you versus what is happening around you.
4. Knocking Over Art: This action may represent feelings of guilt or anxiety about making mistakes or causing disruption in your life or others'. The reaction of the art students could symbolize your fears about being judged or criticized for your actions.
5. Brutalist Building: Such architecture can evoke feelings of harshness or rigidity. This might reflect how you perceive certain situations in your life—perhaps feeling stuck or constrained by outside expectations.

Overall, your dream suggests a need to confront unresolved emotions, address personal priorities, and consider the impact of your actions on yourself and others. It may be beneficial to reflect on these themes in your waking life and contemplate any changes you might want to make.