Installing or removing from the sink Grohe Europlus faucet.

I would remove the handle and escutcheon plate and grab the front of the faucet cartridge with pliers and see if it is hard to turn now. If it is then there must be an issue with the handle being on too tight or it is binding with with the escutcheon plate somehow. If the cartridge is hard to turn after removing the handle etc. I would pull the cartridge out and grease it using heat proof grease (Plumber's grease) and reinstall it. Make not of it's position when you remove it so as to reinstall in the same position. There isn't any reason I can think of other than the above for the faucet to not turn easy.

The hose should simply unscrew from the back of the head.

Here is the page on the Grohe site:

http://www.grohe.com/us/15219/kitchen/kitchen-faucets/ladylux/product-details/?product=33755-G077&color=SDE&material=33755SD0&~[ajax]=33063

shut off water supply knobs remove hoses with pipe or crescent wrench at the base of the faucet under the sink and knob connections

yes, i replaced my american standard hose it was a lot of work to get new hose down the facuat body, you can go to their website and get part number and price for hose. my amercian standard hose was about the cost of a new facuat, so i adapted a differebt make to fit with reducers and nipples.

Found Diagram on the web

when you installed did any teflon tape or debris get inside? you can remove and reverse flush with hose and it may clear the blockage

there is a couple of plates with a little screw in the center that tightens up the plate got to tighten it up

go to the store you bought it and see if they carry parts. if not , try the internet under grohe.com.

remove aerator and cart. and soak in limeaway over night

There should be an o-ring on the mating surfaces of the hose and the faucet that my be missing.  It could also me that the big washer in side of the faucet (under the cartridge) has been shifted.  
I doubt it is the cartridge itself, always try the cheap ideas first.