Before going too far, what exactly are you looking for in your curtains? Type (Sheers? Darkening? Simply decorative?) What style? What type of fabric? Colors? What type of mounting hardware do you have?
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One thing to consider is your budget. Custom curtains from an interior design company can be eye-wateringly expensive here. Or if you are lucky the cost might be just the fabric plus a reasonable hourly rate if you find an independent sewer who is willing to do them for you.
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At the higher end, Les Tissues Colbert does made to measure curtains:
https://www.lestissuscolbert.com/en/...on-sur-mesure/
Less expensive, Manor does made to measure curtains. Limited fabric selection and style, though.
ETA: Snap, Kri.
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Most dry cleaners offer alterations, and would be able to hem curtains for you if you found some you like that are simply too long.
Many fabric stores offer a Nähservice.
Interior design, or tailoring atelier could all make custom curtains.
Search for 'Vorhänge nach mass Zürich' or Vorhänge Nähservice. If you give us more info as to what exactly you want we can perhaps steer you in a more focused direction.
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Another thought - I am not keen on most of the fabric available in Switzerland - what seems to be popular here is just not my style.
As an alternative, I've found a print on demand company, Spoonflower, with a printer in Berlin. You choose the fabric type, choose the fabric design (they have thousands to choose from) - and they will print the fabric. They will also make curtains, bedding, other household design items if you aren't into sewing yourself. I've bought fabric from them, but never had them make an item.
If you go that route, order a swatch or fat quarter of the designs you like, printed on the various fabrics you are interested in, before buying a large amount of fabric. You need to understand actual color - and repeat, match, hand, etc.
Also, be aware that there would be customs duties. So this really is a 'last resort' suggestion.
https://www.spoonflower.com
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Hemming curtains is a pretty basic sewing skill. Maybe there is an EFer who would be glad of earning a bit to do yours?
(Along those lines - there have been threads where folks hosting refugees have commented at the difficulty some are having finding work. Maybe this could be a project for a refugee with sewing skills?)
So... a bit more info as to what you are looking for might help us better help you...
All the best.
ETA with another idea:
If you have curtains that are what you want but simply too long but cannot sew yourself there is another DIY solution - fusible hemming tape. (Saumvlies in German.) Prym is a manufacturer readily avalable in Switzerland - you can find it at any fabric store (I use Kreando for most of my notions) or even in at galaxus, amazon, or even larger grocery stores. This is only a good solution if you are patient with measuring and ironing, though.