A stroller with a very upright seat and good suspension

Hey, Benjolina,

You will do best looking at reversible seaters with larger frames and wheels, then. Personally, I would suggest checking out the Cybex Talos S which is more robust for worse terrain, and has a very upright seat (I wouldn't say there is a stroller model with exactly 90 degrees backrest, though, but it's close).

Also, Joie reversible pushchairs are quite upright and with larger wheels, look at the Joie versatrax for sure.

Lastly, I have notices the Peg-Pérego reversible strollers are very upright, though I have to say there, the wheels and suspension are not as comfy from my experience, so better to try them out before buying.