If i have issued a one entry schengen visa from german embassy that allow me to visit Italy?

Question

taking in considiration i will visit germany first

Answer 1

Yes, with a Schengen Visa you are allowed to visit every countries of the Schengen ones

Answer 2

No problem!  Schengen visa requirements are that you apply for the visa at the embassy of the country through which you intend to enter th Schengen Zone,or the country in which you anticipate spending the majority of your time.  Therefore, even though you received the visa from the German embassy, you may certainly visit Italy after you have entered through Germany.