If the seats are saggy, there are a few ways to fix them.
Hope that's of some help.........
You can unzip the cushions, pull out the pillows inside and fluff them up. I had no idea I could do this to my back couch cushions because they are attached to the couch, but found zippers hidden underneath. If fluffing the cushions and placing back in doesn't help, you can always add new foam and batting.
You can buy special folding frames to put under the cushions, but my friends just put a piece of plywood under their sagging cushions.
Hi Brenda! Here are some great ideas to do this!
This should help: https://lifehack.media/how-to-fix-saggy-couch-cushions