Depreciation: Occupancy Utilization of Laptop Rises Next Year?

I'm currently working on the ESt statement from my friend. He works as a media designer and also completes a distance learning course in graphic design. In 2017 he had to buy a Macbook because of his distance learning. (This course of study is designed to). In the ESt-Explan. In 2017, his Macbook was 50% professionally recognized. However, his professional part has increased in 2018, I have evidence. I would like to schedule the laptop with 80% professional use. The laptop should be written off over 3 years (from Sep. 2017). How do you calculate the new depreciation? Do I withdraw the already written off in 2017 and rewrite the remaining amount with 80%?

You take the depreciation amount for 2018 and take it 0.8 times

Thank you for your prompt reply!

You have to have a 100% amount that you would write off for 2018 if he used it 100%

you just take it 0.8 times

How many years did you want to write off the book and how, linear?

On 3 years, he bought the laptop in Sept. 2017 for 3,168.43 euro.

With your statement, you should be very careful. According to Steuerberatungsgesetz you are not allowed to give a "friend" any businesslike help in tax matters. That can have bad consequences. Delete the question best.