Good Morning Miss Bahor,
Thank you for your questions.
Mattress toppers are predominantly used to protect a mattress but will also soften down any firm feeling mattress.
You are correct that mattress toppers are added where more comfort is required. Unfortunately, a mattress topper will not do the opposite and firm up the mattress.
My advice would be to check what type of base the existing mattress is on as it could be a pocket sprung unit meaning that it’s being softened down. It could also be a Sprung Slatted base in which case you could try placing some sheets of MDF over the slats to firm it up.
Other than that there isn’t much else you can do and our advice here would be to purchase a new mattress, a new base or both.
I hope that this has answered your questions fully but if you do have any further queries then please don’t hesitate to contact our office on 0161 437 4419.
Kind Regards Julie