I can understand most of the text when it is in German, but I feel totally weak to write or speak in German. I need training. Is there a site that offers sentences in English - of a kind of complexity and not as every day patterns of speaking - together with their translation?
Have you tried looking for 'side-by-side' or 'parallel' texts? A Google search using those terms plus the two languages yields a lot of options at many different levels of complexity!
Some examples of varying levels of complexity of English/German parallel texts can be found at:
If that fails you, you can always make your own version of a parallel text simply by finding a text in your native language, getting the German version, and reading the two side-by-side! I find it especially helpful to do this with texts I'm already very familiar with in my native language so that I can pretty accurately guess what the sentences mean in German and practice the grammar in a natural, passive way, but have my original there to guide me if things get too complex.