Used 2018 Chevrolet Silverado 1500 LT Z71 for Sale near Nunavut

Check engine light came on. Scan the codes. Codes were P0326,P0700,P02723. Changed transmission fluid and filter, Cleaned the pan and transmission fluid didn’t look bad. Put it all together. Took it for a test drive ((no check engine light)) and noticed once I was getting close to 35 mph the RPM would shoot to 4000. Unplugged the battery overnight hoping it would reset any computer issues . Turn it on the next morning put it in reverse and noticed I had to push the pedal a little harder and took higher RPM just to reverse or to go forward. Cleaned the throttle body and I’m still having this issue . Any Advice?