When I personally saw the CBSE 2019 Physics Question paper, I found that the questions were not really tough, but  the question paper as a whole was very lengthy. 3 hours time is not sufficient to complete the paper. It is expected that CBSE will be lenient in correcting the physics paper and along with that, will reward appropriate grace marks to all the candidates. You have attempted 50 marks out of 70, I can say with confidence and from my experience, you will get 55/70 or more in theory and in practicals your teachers will give you 30 marks. So, dont worry you will secure a minimum of 85 marks in total, which is good.
What you should do now?

1. Forget about the paper
Almost all the candidates faced the same problem. Physics paper was lengthy. Now its the time to relax and forget about it.
2. Focus on upcoming exams
With a fresh mind, start preparing for the upcoming. One paper should not affect your entire exam.