Turning a couch into a loveseat

I don't see how that would work.

It really depends on the structure of your couch. First thing you will need to get it somewhere where you won't mind making a mess. If it is just a wood frame you can probably just use a reciprocating saw to cut out the center and then simply attach the two sides together in the middle. I would add support though across the entire center (on the underside both front and back) or it will probably sag over time.

Without seeing your existing couch, we can't give you any ideas of how you could transform it into a smaller piece of furniture.

Settees are back in fashion, the kind with a back on only part of the couch. You could cut off the end of your sofa, saving the legs, and leaving the frame the length you want. Then cut off the back, just above the frame for the seats, leaving the other arm of your sofa intact. Sand and stain/paint all the wooden parts. If you decided to replace the sofa cushions, including the back, the remaining arm, and any other upholstered parts, take them off the sofa carefully and use each part for the new upholstery, except you might want one long cushion for the seat. You could even saw the remaining back frame to a romantic curve, and make the upholstery fit. Best wishes ☺️