The answer to 'why do I have mouse' is that mice are common household pests that can enter your home in search of food, water, and shelter. Mice are attracted to crumbs, spills, pet food, and other easily accessible food sources. They may also find their way in through cracks, holes, or other openings in your home's exterior. Signs of a mouse problem include droppings, gnaw marks, nests, and the sightings of mice themselves.
To get rid of mice, you'll need to remove their food sources, seal up entry points, and use humane traps or baits. If the infestation is severe or you have difficulty eliminating the problem, it's best to call a professional pest control service. They have the expertise and tools to properly identify and treat the issue.