Tips to clean Bauknecht oven

Do you have any nice tips to clean the Bauknecht oven in our apartment? There is a lot of black stuff on the floor of the oven -- we got the apartment only a couple of months back. There is smoke sometimes (especially from the floor) when we cook in the oven.

I am new to the developed world and that's why I wanted some best practices to know how to clean, what should be the frequency of cleaning, how to save electricity with the oven, etc. We use the oven around 7-8 times in a week. Thank you in advance.