Welcome to T Nation mane.
You are new to sumo so I think it’d be more helpful to link you to some helpful guides on pulling sumo instead of doing a formcheck and telling you to fix a whole boatload of things.
Formcheck is more helpful when you’re closer to good technique and then the forum can help you get from good to great technique, just ask @guineapig or have a look at his training log, as opposed to going from rubbish to good which you can do yourself effectively.
I’ll link you some vids so watch, learn and apply (maybe apply one thing at a time tho because you could get overwhelmed trying to apply hours worth of info at once). Will give you some thoughts on your current form so you have some idea as to where your focus should be.
There’s a lot more resources out there tho so if one cue doesn’t work look for another. Stuff you should be working on / looking at include:
Set Up is pretty much the most important aspect of the lift. Achieving a good starting position will let you lift more safely. Watch the vids and learn how to set up especially in relation to opening up your hips.
Bracing your back properly so minimize rounding. For some a simple cue is enough like “pull the bar into you”, “cover your armpits with your arm as tho to prevent someone tickling you” or my personal favourite which is to externally rotate your shoulders/elbow i.e. to apply a small torque to the bar from the shoulder.