Our yard is nothing but weeds. We live in Iowa.

It would be best to start over,rototill and remove any weeds etc.level out the area with top soil, lime, seed for you location, top with starter fertilizer and peat moss, keep moist until the seed germinates

MAYBE YOU SHOULD START BY DRAWING A PLAN OF WHAT YOU WOULD LIKE TO SEE IN YOUR YARD AND WHERE THAT YOU BOTH AGREE ON. tHEN GO ABOUT MAKING IT REALITY........

I agree with both of the above. Make your plan, impliment In stages. Do get the weeds out before seeding grass. Some grass seed may come with an extra filler paper like to help the seed along. It may seem thin at first,,,it will fill in.

My inclination would be to ”kill” everything in the backyard first,then add new soil to level etc then plant seed or new sod

My lawn is full of weeds too. I suggest starting in stages As posters suggest above. Depending upon your lot size you can be overwhelming situation. Do your adjacent neighbors have weeds?

What size of lawn do you have. What is your final plan for the lawn. First thing you should do is to remove the weeds. Wait till a day when it is raining or put sprinkler on lawn for a 30 minutes. Take your shovel and dig up the yard. You don't have to do it all at once if it is a big yard.

If you live in the United States you can buy Weed and Feed that attaches to your hose or in granular size that you apply with a spreader. Go to Home Depot or Lowes and ask at the Garden Centre what is the easiest thing to do. Read the directions when applying and do not apply on a windy day, you might kill a neighbours lawn or garden.

After you get rid of the weeds, rent a rototiller, till the area and rake until the ground is level.