Challenge is Argos* own brand. It likely has the typical BSO problems - unbranded components made of cheese that are impossible to adjust correctly and last just long enough for it to go in the shed rather than be taken back to the shop; bearings that don't stay round for very long; etc. The listed weight is 13.5 kg, which is approximately one ton. The geometry doesn't look great (short wheelbase) and the chainring looks tiny for a small-wheeled bike if you have any intention of making progress.
The frame is likely solid and if you're prepared to replace a lot of the components (pedals, brakes, bottom bracket, hubs, chainset, saddle, tyres, grips, ...) it might be ok.
(* the book of dreams one, not the other one)