The difference between past time focus and present time focus is that present time focus refers to the moment we are living in, the moment we are going to now. The past focus is that we are paying attention to the things that we have experienced in the past. The basic difference is one things is about being focused on the present situation while the other is thinking about past situations or experiences.
Step-by-step explanation:
Past time focus : David has good marks and he is thinking about that achievement and good grades at that time
Present time focus : David has gotten good grades right now so he is going to put in time to better himself.