WTF 50 days, are they gonna build the whole house again from scratch??
Friends apartment had the Sauna and bathroom renovation done because of moisture in the walls, so the whole thing was taken out, all tiles removed from the walls, walls equalized by sanding, floor (linoleum or something similar) removed, sauna dismantled, windows removed and then all walls and the floor were dried with a special heater / huge fan.
Then the new floor was put in (epoxy that looks like granite

but looks ok) very tough stuff

.
Then the whole sauna was rebuild (including the alu foil) , new insulation new wooden walls, new benches, new window plinths, then the walls were covered with new tiles, the old sink and toilet were placed back old piping used, a new shower was mounted and supplied with new piping, the old heating radiator was replaced for a new one, old piping used. the old sauna door was placed back, all new plinths. Finished from start to end in 26 days by just one man and last day the electrician connecting the electric stuff (with the right equipment).
Of course this was paid for by someone else, not me

(Friend is renting, this is sometimes better than owning

)
So my advise, don't buy... too expensive and takes way too long.