Our shop have been- has
the German market for the car-accessory sales- the German car-accessory sales market
began the elaboration- unclear- do you have the site or are you setting it up?
tires and rims sales- tire and rim sales
the necessary technical description and the high quality digital pictures of the output produced by your company- the necessary tecnical descrtiptions and high-quality digital pictures of your company's products
will give an additional publicity- delete 'an'
as the most important thing- most importantly/most importantly of all
it will assist the increase of sales- will increase the sales of your products
in the digital form,- in digital form/format
your comprehension- cooperation??