My screen for gmod is sideways

Every time i launch gmod i get a sideways screen. not just that but it is completely black. you can still click the stuff and once you fiddle around a bit you can get a game started. then you can see everything all the controls work but it is SIDEWAYS. the Ctrl+Alt+Up Arrow doesn’t work on my gmod it flips like that then a second later it goes sideways again. please give a good answer and not “Just Flip ur Screen”. thank you.

flip it turnways

I don’t think this is an issue with gmod itself… Dd you try to see if other games do this? Did you check if your driver is up to date? Check the driver settings, make sure it isn’t set to turn the screen sideways. Also, what graphics card are you using?