Advice regarding how to soften up a brick hard sofa you just bought by being really, really stupid?

I found myself unexpectedly needing to quickly get a new sofa and in fact I have never bought one before and I was/am skint and also dealing with being ill right now, so that is all to say I was not able to get out to buy one in person and options were a bit limited. So I bought one from Next online (I have included a picture, it was £699). I checked the dimensions which all seemed great for me, but it just did not occur to me at all that the cushions would not be removable OR that they would in fact be brick hard (!). The advice I found re the problem online is mostly all about taking the cushions off and stepping all over them/using your weight basically to loosen up the foam and make them soften, but I can’t do that, they are literally sewn in and immovable. I now realise I should have checked they were removable and also there are no reviews and I now know never to buy a sofa when that’s the case. I will also never buy faux leather again ( or only does it complicate the matter but it is off-gassing like mad, I am even considering using bicarbonate of soda on it overnight). Anyway I was gonna just try to find the heaviest stuff I can and put it on an tray and keep moving it across the seat pads or something but that feels like it would take AGES to change anything, so I was wondering if there was maybe an option of using heat or something? Again, it is faux leather not fabric so that complicates it all. I just really wanna soften this foam up a least a bit. I am stuck with it for now so while it is obviously not gonna be my sofa for years and years, it is the best I will have for a long time. I really appreciate any ideas. I have been using a fluffy blanket to sit on but it slides about and looks messy and just….is not a real solution. It looks fab but is my worst purchase ever and yeh I feel like a total idiot.