I’m having a bit of trouble understanding you. Are you trying to make the bus taller? If so, take each individual part that needs to be taller, and then use the resize tool to stretch it to your desired height.
Try selecting the entire wall by using your cursor with click and drag, individually selecting each part using explorer, or a mix of both, and then moving the entire wall closer to the opposite wall. This way your bus can be thinner.
You could also group all of the selected parts so you won’t have to individually select each part in the future.
If you want it smaller then I would recommend redoing the interior. Bus interiors are usually very small anyways, there doesn’t really need to be much room.
It only needs to be a total of 4/5 chairs wide, and then you can remove the middle chair to make a walkway. Also try to use multiple levels like that bus has with the steps.
Because of the scale of a Robloxian it’s tough to make small spaces like a bus that are entirely real-to-life scale.
When building I make an R6 type model humanoid like you have in your picture using a 1,4,2 stud body & legs, copied and turned into a 1,2,4 arms and body, with a 1,1,2 Part on top with a HeadMesh scaled to 1.25,1.25,1.25. Then I move it around to see how it fits in all the spaces it needs to. But realize that if this were a human they’d be very roughly about 5 feet tall and 4 feet wide.
Also if I build something like a bus, I’d start with 1 Part made the size I want the bus to be, then rough out the walls, floor and roof, then go into Test mode and walk around inside the model to see how it feels. If something isn’t right then it’s much easier to rescale it in the beginning rather than realize it after you’re done and have to redo all your hard work.