how can i scale it up to make it bigger? because when i do it the quality of the image looks bad
I'm not personally familiar with Roblox Studio, but in the engines I use, we typically use a "nine-patch rectangle" for scaling borders or screens. This type of rectangle expands only in specific areas while keeping the borders intact. For example, in the grid below, sections 2, 4, 6, and 8 can stretch, while 1, 3, 7, and 9 remain unchanged.