The most important thing is to start with correct air pressure.
Then there are hangers on each side to adjust. These can get bent.
The front is supposed to be maybe 1/2" lower than the rear I think.
Do you have an operator's manual?
Mower shops have a cheap blade measuring tool for this. Make sure the blades are good and straight.
The wheels need to be adjusted just 1/8-1/4" or so above your normal mowing height when lowered into position on a level surface.
