Hi Monica,
I am afraid that this is a bad dream. It is probably God informing you about the bad and negative spiritual situation in your sister or about either your sister and her family or their congregation, depending on what the trigger was exactly.
To me, it appears that this is all about your sister and her family. All the symbols and the colors are negative that speaks of spiritual deterioration (disorderly with clothes and things just scattered in the living room) (scattered clothes also speak of them disregarding and not respecting being spiritually prepared for life or for life or ministry), spiritual chaos, and spiritual destruction. Some of it can even be physical like financial destruction is well.
You being naked probably speaks of you feeling unprepared in this particular situation to help them.
The hot shower and the bath both speak of them needing to repent urgently and immediately (of specific sins in their lives) otherwise they will reap the consequences of their actions and behavior. The fact that the hot water was in the shower and not the bath probably speaks of them being Christians already but that they need to repent of specific sins. Please let me know if I am correct here.
The yellow shirt speaks of jealousy, conflict, and even hate. So this played a part in the heart of your sister as it belongs to her. She prepared herself to be jealous about something and this is what caused a lot of the spiritual chaos. The dirt on the floor speaks of a particularly bad sin (could be sexual but not necessarily) that is probably the basis of the spiritual chaos as it was on the floor (foundation level).
You attempting to tidy up speaks of you attempting to help them spiritually probably through counseling.
You wanting to prepare them food speaks of you providing them the word of God (spiritual food). The fact that it is pizza speaks of it being the fundamental basic truths (bread, cheese (comes from milk), and little pieces of meat) neatly put together to be as delicious as possible so that they will eat. Almost like parents in real-life giving their childer veggies concealed among other delicious food just to get them to eat it. You are therefore making the gospel and foundational truths as attractive as possible to get them to repent and follow Christ.
The three slices of pizza speak of getting them to get the harmony of God back in their household. In dreams and visions, the number three symbolizes harmony and one accord. It is the number of the Godhead. It speaks of completeness and the perfect testimony.
Your brother-in-law plays a serious negative part in the situation. He caused a lot of conflict and hate and conflict and dissension, as symbolized by the red truck. In this case, the truck speaks of his motivation in this regard. The truck is old and damaged and word and longer than a normal truck speaks of him doing it for quite a while and him causing quite a lot of damage in the lives of his family.