I have a question why is the website slowly loading?
And if I click on a configured product I get only a picture and not the rest of the info?
there are many reasons Magento can be slow. From a slow server to a screwed up theme or extension. It's impossible to help you without at least URL to a page which loads slow for you.
I do not see any issues with this page: http://www.webpagetest.org/result/170601_M2_1DSQ/
full load speed is fine and first-byte time is fine. you just need to enable browser
I do see a problem on a product page like this: http://www.s4.demohosting4you.nl/t-shirts/uc101.html
it loads fast but shows only product image. this is most likely a problem with the theme you are using. try switching to a default magento theme to see if that product page will load properly. If it will - the problem is with the theme you are using. if default theme will not work as well - the problem can be with some extension causing an error and preventing the rest of the page from loading.
Where i find that: you just need to enable browser caching.
and this is the template: rwd
thank you in advance for the help.
> Where i find that: you just need to enable browser caching.
that depends on your server configuration. you can find some options here or just ask your host to do this for you:
> and this is the template: rwd
this is a default magento theme which somebody customized for you. You can ask your developer to temporary restore all the default files to test and see if the problem is with the changes to the theme or some extension.