It is fairly easy to do DIY, especially if it is already falling down. Any brico store has this soapy type product, mix with water, apply, take down wallpaper.
The bigger issue may be the state of the walls behind the wallpaper? We took down all the wallpaper in the rooms of our place, only to discover mismatched walls with alot of unsmooth surfaces, which required a lot of repairing before painting.
If the walls are in good shape, pretty easy to DIY. If not, check the marketplace section of EF for a handyman.
It would take 39hours and 10 minutes and would cost Chf 4'995.62 + 7.6% TVA
Count about Chf 600.-- per day for a qualified painter with his own tools and van for an 8.5 hour day, how long it will take??? all depends what needs doing once the old wallpaper is off and how mnuchg preparation work there is to do. The actual painting nad papering is not so long, once th epreparation has been done properly.
The Sfr 600.-- per day is for a real self employed painter who has his own insurances, pays pension fund contributions, VAT and any other obligatory social costs A jack of all trades you could get for Chf 300 per day, but ask Mrs Dolittle how jack of all trade gardeners are.....
If the Jack of all trades really screws up, as the tennant you are responsible towards the landlord.
If you plan to do this yourself, I've heard its well worth using a wallpaper steamer - about GBP20 from Amazon. Apparently this stands a much better chance of not damaging the underlying walls.
Also, matt paint can hide a lot of surface imperfections - whereas satin or gloss paint will really highlight them, as I found out by experience when I renovated a kitchen back in the Uk
at a guess if you supplyed materials , i could strip paper in 2 days and paint all wall in 10 hours , based on my own appartment of the same size , providing the walls dont need fixing .30 hrs ish
and at my rates it would be around 1200chf for time alone
be aware of profi swiss painters , a friend of mines apartment cost 18000CHF for painting only its about 180 mtrs took the guy about 1 month ......