Hello,
Indeed your leather is well damaged, but we have seen worse! The good news is that the tears are not at the seams.
To repair your tears you will need to make a lamination with a larger piece of leather at least 4 or 5 cm thick. You will therefore need 2 pieces of leather (one for each side).
RepaCuir (repair paste) fills cracks but also acts as a glue if it is in contact only with leather. You will need at least 4 tubes. When too much leather is missing, as is the case with the more or less round tear, the ideal would be to also put another piece of leather back on top of the one that allowed you to do the laminating. Cut the edges of the torn leather, and adjust the piece of leather to be glued as best you can. Fill the corners with the repair paste.
Generally speaking, the less leather repair paste you put on the surface, the better!
Once your repair is done, you will need to recolour the entire seat with this kit