Seeking for answers from Dutch :(

Welcome on board 

You want to own or start a business in the fitness industry and you expect that your customers, business partners, suppliers etc speaking English with you ? 
Your need the language in any case, not only on daily basis but for your business as well.
German is not Dutch and you would not come far in the Netherlands and as you already started with this language why don't you try Germany?

My daughter was going to do something similar when she first moved back to Holland; it never worked out for her.  Basically, there is no shortage of Gyms or licensed Personal Trainers in Holland; so it's probably not a good idea to move to another country where you don't speak the native language, with this as the cornerstone of your life.

What qualifications do you have as a fitness trainer?  Without a recognised diploma, you will find it very difficult being taken on by any gym in the UK.

Hi! Good to hear that you are thinking about coming to Holland. Here is your requested answer from a Dutchie :-). My opinion: in the bigger cities (Amsterdam, Rotterdam, The Hague) it wouldn't be a problem if you only speak English. Especially in Amsterdam, where there are a lot of expats & international start-up community. Also, a lot of companies are looking for IT staff, so if the fitness doesn't work out you can always do that! Good luck!

Hello again thanks for replies , you are amazing guys ! I've realized I've forgot to mention my question was about Amsterdam as most international city to make things clear I've just fall in love with Dutch culture and want to slowly learn to speak Dutch language, but as this may take a while I was curious if there is a real chance to do personal trainer ( mostly as my own bussines , looking for clients alone and using gym to train them, also doing pc repair and other services  ) as an English speaking person for time I do learn to speak Dutch to be confident enought also if there is social life with other expats and dutchies ( and of course night life while only speaking English language . As I was living a year in Germany and for English speaking person therefore was life very hard as most of the people in bussines or personal life was not interested to speak with me because of my lack of Deutsch thank you guys again for reply, you helped me more then I was expecting

Gyms from my knowledge use their own trainers so I guess they wouldn't want someone else treading on their toes so to speak. It would be better if you found a gym that did not have their own program. But I guess that would be hard to find unless you contacted every Gym.

In my gym there's a personal trainer working independently and he doesn't speak dutch either so that shouldn't be a problem. There a lot of competition though.
As for a IT: you can always combine that. I think OGD ict diensten hires expats.

Hi there! Just being curious: which aspects of Dutch culture did you actually fall in love with?