A polarizer filter should be put on the front of your lens for a start. Many of us leave those on all the time, they are a cheap way to protect the front of the real lens from everyday dirt and scratches.
You camera should have a Neutral Density ( N.D.) filter setting, basically, sunglasses for your lens. There are aftermarket add-ons if you need more of that.
You can also reduce brightness a bit by adding more shutter, say 1/100, however, this can add temporal side effects to motion in the footage that may become objectionable, the higher you crank the shutter.
Use manual iris controls, always. And get some shade over the situation: when you have a crew and a good gaffer truck, you can fly a sort of large square frame of silk diffusion, called a “butterfly”, that will cut the harsh aspects of the sun and bring the levels down a bit. IF you’re of more modest means, any old thing like a patio unbrella clamped to a ladder could be pressed into service.